diff --git a/CHANGELOG.md b/CHANGELOG.md
index 17bf98fc..ae2c2fdc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 Changes for users of the library currently on `develop`:
 
+- Fixed some tests, added tests for NYTPhotoViewerSinglePhotoDataSource
+- Fixed a strict warning and a subscripting bug in NYTPhotoViewerArrayDataSource.m
+- Added support for interstitial views
+
+## [2.0.0](https://github.com/NYTimes/NYTPhotoViewer/releases/tag/2.0.0)
+
+Changes for users of the library in 2.0.0:
+
 - Expose a data-source-oriented API for PhotosViewController ([#226](https://github.com/NYTimes/NYTPhotoViewer/pull/226))
     - A data source no longer has to handle out-of-bounds indexes ([#227](https://github.com/NYTimes/NYTPhotoViewer/pull/227))
     - The data source is not retained ([#227](https://github.com/NYTimes/NYTPhotoViewer/pull/227))
diff --git a/Example-Swift/Photo.swift b/Example-Swift/Photo.swift
deleted file mode 100644
index 630b1025..00000000
--- a/Example-Swift/Photo.swift
+++ /dev/null
@@ -1,19 +0,0 @@
-//
-//  Photo.swift
-//  NYTPhotoViewer
-//
-//  Created by Chris Dzombak on 2/2/17.
-//  Copyright © 2017 NYTimes. All rights reserved.
-//
-
-import UIKit
-
-/// A photo may often be represented in a Swift application as a value type.
-struct Photo {
-    // This would usually be a URL, but for this demo we load images from the bundle.
-    let name: String
-    let summary: String
-    let credit: String
-
-    let identifier: Int
-}
diff --git a/Example-Swift/PhotoBox.swift b/Example-Swift/PhotoBox.swift
index 48c9d46c..58e3046e 100644
--- a/Example-Swift/PhotoBox.swift
+++ b/Example-Swift/PhotoBox.swift
@@ -12,10 +12,10 @@ import NYTPhotoViewer
 /// A box allowing NYTPhotoViewer to consume Swift value types from our codebase.
 final class NYTPhotoBox: NSObject, NYTPhoto {
 
-    let value: Photo
+    let value: PhotoItem
 
-    init(_ photo: Photo) {
-        value = photo
+    init(_ photoItem: PhotoItem) {
+        value = photoItem
     }
 
     // MARK: NYTPhoto
@@ -24,6 +24,14 @@ final class NYTPhotoBox: NSObject, NYTPhoto {
     var imageData: Data?
     var placeholderImage: UIImage?
 
+    var isPhoto: Bool {
+        return value.itemType == .image
+    }
+
+    var isView: Bool {
+        return value.itemType == .view
+    }
+
     var attributedCaptionTitle: NSAttributedString?
 
     var attributedCaptionSummary: NSAttributedString? {
diff --git a/Example-Swift/PhotoItem.swift b/Example-Swift/PhotoItem.swift
new file mode 100644
index 00000000..a1169c81
--- /dev/null
+++ b/Example-Swift/PhotoItem.swift
@@ -0,0 +1,34 @@
+//
+//  PhotoItem.swift
+//  NYTPhotoViewer
+//
+//  Created by Chris Dzombak on 2/2/17.
+//  Copyright © 2017 NYTimes. All rights reserved.
+//
+
+import UIKit
+
+/// A photo item can either be an image or a view
+enum PhotoItemType {
+    case image
+    case view
+}
+
+/// A photo may often be represented in a Swift application as a value type.
+struct PhotoItem {
+    // This would usually be a URL, but for this demo we load images from the bundle.
+    let name: String
+    let summary: String
+    let credit: String
+    let itemType: PhotoItemType
+    let identifier: Int
+
+    init(name: String = "", summary: String = "", credit: String = "", itemType: PhotoItemType, identifier: Int) {
+        self.name = name
+        self.summary = summary
+        self.credit = credit
+        self.itemType = itemType
+        self.identifier = identifier
+    }
+
+}
diff --git a/Example-Swift/PhotoViewerCoordinator.swift b/Example-Swift/PhotoViewerCoordinator.swift
index ae25b91a..2883f4e8 100644
--- a/Example-Swift/PhotoViewerCoordinator.swift
+++ b/Example-Swift/PhotoViewerCoordinator.swift
@@ -9,7 +9,7 @@
 import NYTPhotoViewer
 
 /// Coordinates interaction between the application's data layer and the photo viewer component.
-final class PhotoViewerCoordinator: NYTPhotoViewerDataSource {
+final class PhotoViewerCoordinator: NSObject, NYTPhotoViewerDataSource {
     let slideshow: [NYTPhotoBox]
     let provider: PhotosProvider
 
@@ -20,15 +20,18 @@ final class PhotoViewerCoordinator: NYTPhotoViewerDataSource {
     init(provider: PhotosProvider) {
         self.provider = provider
         self.slideshow = provider.fetchDemoSlideshow().map { NYTPhotoBox($0) }
+        super.init()
         self.fetchPhotos()
     }
 
     func fetchPhotos() {
         for box in slideshow {
-            provider.fetchPhoto(named: box.value.name, then: { [weak self] (result) in
-                box.image = result
-                self?.photoViewer.update(box)
-            })
+            if box.isPhoto {
+                provider.fetchPhoto(named: box.value.name, then: { [weak self] (result) in
+                    box.image = result
+                    self?.photoViewer.update(box)
+                })
+            }
         }
     }
 
@@ -36,7 +39,24 @@ final class PhotoViewerCoordinator: NYTPhotoViewerDataSource {
 
     @objc
     var numberOfPhotos: NSNumber? {
-        return NSNumber(integerLiteral: slideshow.count)
+        return NSNumber(integerLiteral: slideshow.filter({ $0.isPhoto }).count)
+    }
+
+    @objc
+    func numberOfInterstitialViews() -> NSNumber {
+        return NSNumber(integerLiteral: slideshow.filter({ $0.isView }).count)
+    }
+
+    @objc
+    func isPhoto(at idx: Int) -> Bool {
+        guard idx < slideshow.count else { return false }
+        return slideshow[idx].isPhoto
+    }
+
+    @objc
+    func isInterstitialView(at idx: Int) -> Bool {
+        guard idx < slideshow.count else { return false }
+        return slideshow[idx].isView
     }
 
     @objc
@@ -48,6 +68,7 @@ final class PhotoViewerCoordinator: NYTPhotoViewerDataSource {
     @objc
     func photo(at index: Int) -> NYTPhoto? {
         guard index < slideshow.count else { return nil }
+        guard slideshow[index].isPhoto else { return nil }
         return slideshow[index]
     }
 }
diff --git a/Example-Swift/PhotosProvider.swift b/Example-Swift/PhotosProvider.swift
index e5dc437b..416c5367 100755
--- a/Example-Swift/PhotosProvider.swift
+++ b/Example-Swift/PhotosProvider.swift
@@ -10,11 +10,11 @@ import UIKit
 
 /// A component of your data layer, which might load photos from the cache or network.
 final class PhotosProvider {
-    typealias Slideshow = [Photo]
+    typealias Slideshow = [PhotoItem]
 
     /// Simulate a synchronous fetch of a slideshow, perhaps from a local database.
     func fetchDemoSlideshow() -> Slideshow {
-        return (0...4).map { demoPhoto(identifier: $0) }
+        return (0...7).map { [2,5].contains($0) ? demoView(identifier: $0) : demoPhoto(identifier: $0) }
     }
 
     /// Simulate fetching a photo from the network.
@@ -29,7 +29,7 @@ final class PhotosProvider {
 }
 
 extension PhotosProvider {
-    fileprivate func demoPhoto(identifier: Int) -> Photo {
+    fileprivate func demoPhoto(identifier: Int) -> PhotoItem {
         let photoName: String
         let photoSummary: String
         let photoCredit: String
@@ -44,6 +44,10 @@ extension PhotosProvider {
             photoCredit = "Photo: Nic Lehoux"
         }
 
-        return Photo(name: photoName, summary: photoSummary, credit: photoCredit, identifier: identifier)
+        return PhotoItem(name: photoName, summary: photoSummary, credit: photoCredit, itemType: .image, identifier: identifier)
+    }
+
+    fileprivate func demoView(identifier: Int) -> PhotoItem {
+        return PhotoItem(itemType: .view, identifier: identifier)
     }
 }
diff --git a/Example-Swift/ViewController.swift b/Example-Swift/ViewController.swift
index 85a8f1cf..9152146f 100755
--- a/Example-Swift/ViewController.swift
+++ b/Example-Swift/ViewController.swift
@@ -68,4 +68,15 @@ extension ViewController: NYTPhotosViewControllerDelegate {
     func photosViewControllerDidDismiss(_ photosViewController: NYTPhotosViewController) {
         photoViewerCoordinator = nil
     }
+
+    func photosViewController(_ photosViewController: NYTPhotosViewController, interstitialViewAt index: UInt) -> UIView {
+        let redView = UIView(frame: CGRect(origin: .zero, size: CGSize(width: photosViewController.view.frame.width, height: 200)))
+        redView.backgroundColor = .red
+        redView.autoresizingMask = [.flexibleWidth]
+        return redView
+    }
+
+    func photosViewController(_ photosViewController: NYTPhotosViewController, didNavigateToInterstialView view: UIView, at index: UInt) {
+        view.backgroundColor = .blue
+    }
 }
diff --git a/NYTPhotoViewer.podspec b/NYTPhotoViewer.podspec
index 6fe70c84..9a8f962c 100644
--- a/NYTPhotoViewer.podspec
+++ b/NYTPhotoViewer.podspec
@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
   s.name             = "NYTPhotoViewer"
-  s.version          = "2.0.0"
+  s.version          = "3.0.0"
 
   s.description      = <<-DESC
                        NYTPhotoViewer is a slideshow and image viewer that includes double tap to zoom, captions, support for multiple images, interactive flick to dismiss, animated zooming presentation, and more.
diff --git a/NYTPhotoViewer.xcodeproj/project.pbxproj b/NYTPhotoViewer.xcodeproj/project.pbxproj
index da309f1c..f5d56032 100644
--- a/NYTPhotoViewer.xcodeproj/project.pbxproj
+++ b/NYTPhotoViewer.xcodeproj/project.pbxproj
@@ -10,7 +10,6 @@
 		1110840A1C875B5000699670 /* NYTPhotoViewer.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084091C875B5000699670 /* NYTPhotoViewer.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		111084111C875B5000699670 /* NYTPhotoViewer.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 111084061C875B5000699670 /* NYTPhotoViewer.framework */; };
 		1110842D1C8767BA00699670 /* NYTPhotoCaptionViewTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084261C8767BA00699670 /* NYTPhotoCaptionViewTests.m */; };
-		1110842E1C8767BA00699670 /* NYTPhotosDataSourceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084271C8767BA00699670 /* NYTPhotosDataSourceTests.m */; };
 		1110842F1C8767BA00699670 /* NYTPhotosOverlayViewTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084281C8767BA00699670 /* NYTPhotosOverlayViewTests.m */; };
 		111084301C8767BA00699670 /* NYTPhotosViewControllerTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084291C8767BA00699670 /* NYTPhotosViewControllerTests.m */; };
 		111084311C8767BA00699670 /* NYTPhotoTransitionAnimatorTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 1110842A1C8767BA00699670 /* NYTPhotoTransitionAnimatorTests.m */; };
@@ -35,7 +34,7 @@
 		1110845D1C87682300699670 /* NYTScalingImageView.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084441C87682300699670 /* NYTScalingImageView.m */; };
 		1110845E1C87682300699670 /* NYTPhoto.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084461C87682300699670 /* NYTPhoto.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		1110845F1C87682300699670 /* NYTPhotoCaptionViewLayoutWidthHinting.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084471C87682300699670 /* NYTPhotoCaptionViewLayoutWidthHinting.h */; settings = {ATTRIBUTES = (Public, ); }; };
-		111084601C87682300699670 /* NYTPhotoContainer.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084481C87682300699670 /* NYTPhotoContainer.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		111084601C87682300699670 /* NYTPhotoViewerContainer.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084481C87682300699670 /* NYTPhotoViewerContainer.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		111084611C87682300699670 /* NYTPhotoViewerDataSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084491C87682300699670 /* NYTPhotoViewerDataSource.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		111084621C87682300699670 /* NSBundle+NYTPhotoViewer.h in Headers */ = {isa = PBXBuildFile; fileRef = 1110844B1C87682300699670 /* NSBundle+NYTPhotoViewer.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		111084631C87682300699670 /* NSBundle+NYTPhotoViewer.m in Sources */ = {isa = PBXBuildFile; fileRef = 1110844C1C87682300699670 /* NSBundle+NYTPhotoViewer.m */; };
@@ -79,7 +78,7 @@
 		11FBDA9D1C87753200018169 /* NYTScalingImageView.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084441C87682300699670 /* NYTScalingImageView.m */; };
 		11FBDA9E1C87753200018169 /* NYTPhoto.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084461C87682300699670 /* NYTPhoto.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		11FBDA9F1C87753200018169 /* NYTPhotoCaptionViewLayoutWidthHinting.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084471C87682300699670 /* NYTPhotoCaptionViewLayoutWidthHinting.h */; settings = {ATTRIBUTES = (Public, ); }; };
-		11FBDAA01C87753200018169 /* NYTPhotoContainer.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084481C87682300699670 /* NYTPhotoContainer.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		11FBDAA01C87753200018169 /* NYTPhotoViewerContainer.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084481C87682300699670 /* NYTPhotoViewerContainer.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		11FBDAA11C87753200018169 /* NYTPhotoViewerDataSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 111084491C87682300699670 /* NYTPhotoViewerDataSource.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		11FBDAA21C87753200018169 /* NSBundle+NYTPhotoViewer.h in Headers */ = {isa = PBXBuildFile; fileRef = 1110844B1C87682300699670 /* NSBundle+NYTPhotoViewer.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		11FBDAA31C87753200018169 /* NSBundle+NYTPhotoViewer.m in Sources */ = {isa = PBXBuildFile; fileRef = 1110844C1C87682300699670 /* NSBundle+NYTPhotoViewer.m */; };
@@ -94,7 +93,10 @@
 		11FBDAFD1C877D9A00018169 /* LaunchScreen.xib in Resources */ = {isa = PBXBuildFile; fileRef = 11FBDAFB1C877D9A00018169 /* LaunchScreen.xib */; };
 		11FBDAFE1C877F5500018169 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 111084781C876A2B00699670 /* Assets.xcassets */; };
 		11FBDAFF1C877F8000018169 /* giphy.gif in Resources */ = {isa = PBXBuildFile; fileRef = 111084851C876B0400699670 /* giphy.gif */; };
-		9371A73C1E438B9C00A8F2EF /* Photo.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9371A73B1E438B9C00A8F2EF /* Photo.swift */; };
+		1AFC4D301FE01B9000FDF949 /* NYTPhotoViewerArrayDataSourceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 111084271C8767BA00699670 /* NYTPhotoViewerArrayDataSourceTests.m */; };
+		1AFC4D321FE01EFA00FDF949 /* NYTPhotoViewerSinglePhotoDataSourceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 1AFC4D311FE01EFA00FDF949 /* NYTPhotoViewerSinglePhotoDataSourceTests.m */; };
+		2A4D6135208683990092ED17 /* NYTInterstitialViewController.m in Sources */ = {isa = PBXBuildFile; fileRef = 2A4D6134208683990092ED17 /* NYTInterstitialViewController.m */; };
+		9371A73C1E438B9C00A8F2EF /* PhotoItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9371A73B1E438B9C00A8F2EF /* PhotoItem.swift */; };
 		9371A7441E438BCE00A8F2EF /* PhotoBox.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9371A7431E438BCE00A8F2EF /* PhotoBox.swift */; };
 		9371A7461E43D61E00A8F2EF /* PhotoViewerCoordinator.swift in Sources */ = {isa = PBXBuildFile; fileRef = 9371A7451E43D61E00A8F2EF /* PhotoViewerCoordinator.swift */; };
 		93F45B181E3BB5610093DB93 /* NYTPhotoViewerSinglePhotoDataSource.h in Headers */ = {isa = PBXBuildFile; fileRef = 93F45B161E3BB5610093DB93 /* NYTPhotoViewerSinglePhotoDataSource.h */; settings = {ATTRIBUTES = (Public, ); }; };
@@ -238,7 +240,7 @@
 		111084101C875B5000699670 /* NYTPhotoViewerTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = NYTPhotoViewerTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
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 		111084261C8767BA00699670 /* NYTPhotoCaptionViewTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotoCaptionViewTests.m; sourceTree = "<group>"; };
-		111084271C8767BA00699670 /* NYTPhotosDataSourceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotosDataSourceTests.m; sourceTree = "<group>"; };
+		111084271C8767BA00699670 /* NYTPhotoViewerArrayDataSourceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotoViewerArrayDataSourceTests.m; sourceTree = "<group>"; };
 		111084281C8767BA00699670 /* NYTPhotosOverlayViewTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotosOverlayViewTests.m; sourceTree = "<group>"; };
 		111084291C8767BA00699670 /* NYTPhotosViewControllerTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotosViewControllerTests.m; sourceTree = "<group>"; };
 		1110842A1C8767BA00699670 /* NYTPhotoTransitionAnimatorTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotoTransitionAnimatorTests.m; sourceTree = "<group>"; };
@@ -263,7 +265,7 @@
 		111084441C87682300699670 /* NYTScalingImageView.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTScalingImageView.m; sourceTree = "<group>"; };
 		111084461C87682300699670 /* NYTPhoto.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhoto.h; sourceTree = "<group>"; };
 		111084471C87682300699670 /* NYTPhotoCaptionViewLayoutWidthHinting.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhotoCaptionViewLayoutWidthHinting.h; sourceTree = "<group>"; };
-		111084481C87682300699670 /* NYTPhotoContainer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhotoContainer.h; sourceTree = "<group>"; };
+		111084481C87682300699670 /* NYTPhotoViewerContainer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhotoViewerContainer.h; sourceTree = "<group>"; };
 		111084491C87682300699670 /* NYTPhotoViewerDataSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhotoViewerDataSource.h; sourceTree = "<group>"; };
 		1110844B1C87682300699670 /* NSBundle+NYTPhotoViewer.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSBundle+NYTPhotoViewer.h"; sourceTree = "<group>"; };
 		1110844C1C87682300699670 /* NSBundle+NYTPhotoViewer.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSBundle+NYTPhotoViewer.m"; sourceTree = "<group>"; };
@@ -293,7 +295,10 @@
 		11FBDAEA1C877BD600018169 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
 		11FBDAF01C877C8B00018169 /* PhotosProvider.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PhotosProvider.swift; sourceTree = "<group>"; };
 		11FBDAFC1C877D9A00018169 /* Base */ = {isa = PBXFileReference; lastKnownFileType = file.xib; name = Base; path = Base.lproj/LaunchScreen.xib; sourceTree = "<group>"; };
-		9371A73B1E438B9C00A8F2EF /* Photo.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Photo.swift; sourceTree = "<group>"; };
+		1AFC4D311FE01EFA00FDF949 /* NYTPhotoViewerSinglePhotoDataSourceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = NYTPhotoViewerSinglePhotoDataSourceTests.m; sourceTree = "<group>"; };
+		2A4D6134208683990092ED17 /* NYTInterstitialViewController.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = NYTInterstitialViewController.m; sourceTree = "<group>"; };
+		2A4D613C208683B80092ED17 /* NYTInterstitialViewController.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = NYTInterstitialViewController.h; sourceTree = "<group>"; };
+		9371A73B1E438B9C00A8F2EF /* PhotoItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PhotoItem.swift; sourceTree = "<group>"; };
 		9371A7431E438BCE00A8F2EF /* PhotoBox.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PhotoBox.swift; sourceTree = "<group>"; };
 		9371A7451E43D61E00A8F2EF /* PhotoViewerCoordinator.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = PhotoViewerCoordinator.swift; sourceTree = "<group>"; };
 		93F45B161E3BB5610093DB93 /* NYTPhotoViewerSinglePhotoDataSource.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NYTPhotoViewerSinglePhotoDataSource.h; sourceTree = "<group>"; };
@@ -389,6 +394,8 @@
 				111084401C87682300699670 /* NYTPhotoTransitionController.m */,
 				111084411C87682300699670 /* NYTPhotoViewController.h */,
 				111084421C87682300699670 /* NYTPhotoViewController.m */,
+				2A4D613C208683B80092ED17 /* NYTInterstitialViewController.h */,
+				2A4D6134208683990092ED17 /* NYTInterstitialViewController.m */,
 				111084371C87682300699670 /* NYTPhotoViewerArrayDataSource.h */,
 				111084381C87682300699670 /* NYTPhotoViewerArrayDataSource.m */,
 				93F45B161E3BB5610093DB93 /* NYTPhotoViewerSinglePhotoDataSource.h */,
@@ -406,7 +413,8 @@
 			isa = PBXGroup;
 			children = (
 				111084261C8767BA00699670 /* NYTPhotoCaptionViewTests.m */,
-				111084271C8767BA00699670 /* NYTPhotosDataSourceTests.m */,
+				111084271C8767BA00699670 /* NYTPhotoViewerArrayDataSourceTests.m */,
+				1AFC4D311FE01EFA00FDF949 /* NYTPhotoViewerSinglePhotoDataSourceTests.m */,
 				111084281C8767BA00699670 /* NYTPhotosOverlayViewTests.m */,
 				111084291C8767BA00699670 /* NYTPhotosViewControllerTests.m */,
 				1110842A1C8767BA00699670 /* NYTPhotoTransitionAnimatorTests.m */,
@@ -422,7 +430,7 @@
 			children = (
 				111084461C87682300699670 /* NYTPhoto.h */,
 				111084471C87682300699670 /* NYTPhotoCaptionViewLayoutWidthHinting.h */,
-				111084481C87682300699670 /* NYTPhotoContainer.h */,
+				111084481C87682300699670 /* NYTPhotoViewerContainer.h */,
 				111084491C87682300699670 /* NYTPhotoViewerDataSource.h */,
 			);
 			path = Protocols;
@@ -503,7 +511,7 @@
 				9371A7451E43D61E00A8F2EF /* PhotoViewerCoordinator.swift */,
 				11FBDAF01C877C8B00018169 /* PhotosProvider.swift */,
 				9371A7431E438BCE00A8F2EF /* PhotoBox.swift */,
-				9371A73B1E438B9C00A8F2EF /* Photo.swift */,
+				9371A73B1E438B9C00A8F2EF /* PhotoItem.swift */,
 				11FBDAE21C877BD600018169 /* Main.storyboard */,
 				11FBDAFB1C877D9A00018169 /* LaunchScreen.xib */,
 				11FBDAEA1C877BD600018169 /* Info.plist */,
@@ -520,7 +528,7 @@
 			files = (
 				111084621C87682300699670 /* NSBundle+NYTPhotoViewer.h in Headers */,
 				111084541C87682300699670 /* NYTPhotosViewController.h in Headers */,
-				111084601C87682300699670 /* NYTPhotoContainer.h in Headers */,
+				111084601C87682300699670 /* NYTPhotoViewerContainer.h in Headers */,
 				1110844E1C87682300699670 /* NYTPhotoDismissalInteractionController.h in Headers */,
 				111084611C87682300699670 /* NYTPhotoViewerDataSource.h in Headers */,
 				1110845A1C87682300699670 /* NYTPhotoViewController.h in Headers */,
@@ -542,7 +550,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				11FBDA981C87753200018169 /* NYTPhotoTransitionController.h in Headers */,
-				11FBDAA01C87753200018169 /* NYTPhotoContainer.h in Headers */,
+				11FBDAA01C87753200018169 /* NYTPhotoViewerContainer.h in Headers */,
 				11FBDA9C1C87753200018169 /* NYTScalingImageView.h in Headers */,
 				11FBDA921C87753200018169 /* NYTPhotosOverlayView.h in Headers */,
 				11FBDA8E1C87753200018169 /* NYTPhotoDismissalInteractionController.h in Headers */,
@@ -825,6 +833,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				2A4D6135208683990092ED17 /* NYTInterstitialViewController.m in Sources */,
 				111084591C87682300699670 /* NYTPhotoTransitionController.m in Sources */,
 				111084631C87682300699670 /* NSBundle+NYTPhotoViewer.m in Sources */,
 				111084551C87682300699670 /* NYTPhotosViewController.m in Sources */,
@@ -843,14 +852,15 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				1AFC4D301FE01B9000FDF949 /* NYTPhotoViewerArrayDataSourceTests.m in Sources */,
 				1110842D1C8767BA00699670 /* NYTPhotoCaptionViewTests.m in Sources */,
 				1110842F1C8767BA00699670 /* NYTPhotosOverlayViewTests.m in Sources */,
-				1110842E1C8767BA00699670 /* NYTPhotosDataSourceTests.m in Sources */,
 				111084311C8767BA00699670 /* NYTPhotoTransitionAnimatorTests.m in Sources */,
 				111084301C8767BA00699670 /* NYTPhotosViewControllerTests.m in Sources */,
 				111084841C876AAD00699670 /* NYTExamplePhoto.m in Sources */,
 				111084331C8767BA00699670 /* NYTScalingImageViewTests.m in Sources */,
 				111084321C8767BA00699670 /* NYTPhotoViewControllerTests.m in Sources */,
+				1AFC4D321FE01EFA00FDF949 /* NYTPhotoViewerSinglePhotoDataSourceTests.m in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -892,7 +902,7 @@
 				11FBDADF1C877BD600018169 /* AppDelegate.swift in Sources */,
 				9371A7461E43D61E00A8F2EF /* PhotoViewerCoordinator.swift in Sources */,
 				11FBDAF11C877C8B00018169 /* PhotosProvider.swift in Sources */,
-				9371A73C1E438B9C00A8F2EF /* Photo.swift in Sources */,
+				9371A73C1E438B9C00A8F2EF /* PhotoItem.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/NYTPhotoViewer/NYTInterstitialViewController.h b/NYTPhotoViewer/NYTInterstitialViewController.h
new file mode 100644
index 00000000..b038134b
--- /dev/null
+++ b/NYTPhotoViewer/NYTInterstitialViewController.h
@@ -0,0 +1,31 @@
+//
+//  NYTInterstitialViewController.h
+//  NYTPhotoViewer
+//
+//  Created by Howarth, Craig on 4/17/18.
+//  Copyright © 2018 NYTimes. All rights reserved.
+//
+
+@import UIKit;
+#import "NYTPhotoViewerContainer.h"
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ *  The view controller controlling the display of a interstitial view.
+ */
+@interface NYTInterstitialViewController : UIViewController <NYTPhotoViewerContainer>
+
+/**
+ *  The designated initializer that takes an interstitial view.
+ *
+ *  @param view      The view object that this view controller manages.
+ *  @param itemIndex The index of this view controller in the photo viewer collection.
+ *
+ *  @return A fully initialized object.
+ */
+- (instancetype)initWithView:(nullable UIView *)view itemIndex:(NSUInteger)itemIndex NS_DESIGNATED_INITIALIZER;
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/NYTPhotoViewer/NYTInterstitialViewController.m b/NYTPhotoViewer/NYTInterstitialViewController.m
new file mode 100644
index 00000000..688a045c
--- /dev/null
+++ b/NYTPhotoViewer/NYTInterstitialViewController.m
@@ -0,0 +1,75 @@
+//
+//  NYTInterstitialViewController.m
+//  NYTPhotoViewer
+//
+//  Created by Howarth, Craig on 4/17/18.
+//  Copyright © 2018 NYTimes. All rights reserved.
+//
+
+#import "NYTInterstitialViewController.h"
+#import "NYTPhoto.h"
+
+@interface NYTInterstitialViewController ()
+
+@property (nonatomic, nullable) id <NYTPhoto> photo;
+@property (nonatomic, nullable) UIView *interstitialView;
+@property (nonatomic) NSUInteger photoViewItemIndex;
+
+- (instancetype)initWithCoder:(NSCoder *)aDecoder NS_DESIGNATED_INITIALIZER;
+
+@end
+
+@implementation NYTInterstitialViewController
+
+#pragma mark - UIViewController
+
+- (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
+    return [self initWithView:nil itemIndex:0];
+}
+
+- (instancetype)initWithCoder:(NSCoder *)aDecoder {
+    self = [super initWithCoder:aDecoder];
+
+    if (self) {
+        [self commonInitWithView:nil itemIndex:0];
+    }
+
+    return self;
+}
+
+- (void)viewDidLoad {
+    [super viewDidLoad];
+
+    [self.view addSubview:self.interstitialView];
+    self.interstitialView.center = CGPointMake(CGRectGetMidX(self.view.bounds), CGRectGetMidY(self.view.bounds));
+}
+
+- (void)viewWillLayoutSubviews {
+    [super viewWillLayoutSubviews];
+
+    self.interstitialView.center = CGPointMake(CGRectGetMidX(self.view.bounds), CGRectGetMidY(self.view.bounds));
+}
+
+- (BOOL)prefersHomeIndicatorAutoHidden {
+    return YES;
+}
+
+#pragma mark - NYTPhotoViewController
+
+- (instancetype)initWithView:(UIView *)interstitialView itemIndex:(NSUInteger)itemIndex {
+    self = [super initWithNibName:nil bundle:nil];
+
+    if (self) {
+        [self commonInitWithView:interstitialView itemIndex:itemIndex];
+    }
+
+    return self;
+}
+
+- (void)commonInitWithView:(UIView *)interstitialView itemIndex:(NSUInteger)itemIndex {
+    _photo = nil;
+    _photoViewItemIndex = itemIndex;
+    _interstitialView = interstitialView;
+}
+
+@end
diff --git a/NYTPhotoViewer/NYTPhotoCaptionView.m b/NYTPhotoViewer/NYTPhotoCaptionView.m
index 7f6c83b4..7c28299c 100644
--- a/NYTPhotoViewer/NYTPhotoCaptionView.m
+++ b/NYTPhotoViewer/NYTPhotoCaptionView.m
@@ -58,7 +58,7 @@ - (void)didMoveToSuperview {
 - (void)layoutSubviews {
     [super layoutSubviews];
 
-    void (^updateGradientFrame)() = ^{
+    void (^updateGradientFrame)(void) = ^{
         self.gradientLayer.frame = self.layer.bounds;
     };
 
diff --git a/NYTPhotoViewer/NYTPhotoDismissalInteractionController.h b/NYTPhotoViewer/NYTPhotoDismissalInteractionController.h
index 0029f987..bbaf5a7d 100644
--- a/NYTPhotoViewer/NYTPhotoDismissalInteractionController.h
+++ b/NYTPhotoViewer/NYTPhotoDismissalInteractionController.h
@@ -41,4 +41,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-NS_ASSUME_NONNULL_END
\ No newline at end of file
+NS_ASSUME_NONNULL_END
diff --git a/NYTPhotoViewer/NYTPhotoTransitionController.h b/NYTPhotoViewer/NYTPhotoTransitionController.h
index 68b5d2c8..f7b52669 100644
--- a/NYTPhotoViewer/NYTPhotoTransitionController.h
+++ b/NYTPhotoViewer/NYTPhotoTransitionController.h
@@ -41,4 +41,4 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
-NS_ASSUME_NONNULL_END
\ No newline at end of file
+NS_ASSUME_NONNULL_END
diff --git a/NYTPhotoViewer/NYTPhotoViewController.h b/NYTPhotoViewer/NYTPhotoViewController.h
index 73906f20..95ef1aa1 100644
--- a/NYTPhotoViewer/NYTPhotoViewController.h
+++ b/NYTPhotoViewer/NYTPhotoViewController.h
@@ -7,7 +7,7 @@
 //
 
 @import UIKit;
-#import "NYTPhotoContainer.h"
+#import "NYTPhotoViewerContainer.h"
 
 @class NYTScalingImageView;
 
@@ -24,7 +24,7 @@ extern NSString * const NYTPhotoViewControllerPhotoImageUpdatedNotification;
 /**
  *  The view controller controlling the display of a single photo object.
  */
-@interface NYTPhotoViewController : UIViewController <NYTPhotoContainer>
+@interface NYTPhotoViewController : UIViewController <NYTPhotoViewerContainer>
 
 /**
  *  The internal scaling image view used to display the photo.
@@ -50,12 +50,13 @@ extern NSString * const NYTPhotoViewControllerPhotoImageUpdatedNotification;
  *  The designated initializer that takes the photo and activity view.
  *
  *  @param photo              The photo object that this view controller manages.
+ *  @param itemIndex          The index of this view controller in the photo viewer collection.
  *  @param loadingView        The view to display while the photo's image loads. This view will be hidden when the image loads.
  *  @param notificationCenter The notification center on which to observe the `NYTPhotoViewControllerPhotoImageUpdatedNotification`.
  *
  *  @return A fully initialized object.
  */
-- (instancetype)initWithPhoto:(nullable id <NYTPhoto>)photo loadingView:(nullable UIView *)loadingView notificationCenter:(nullable NSNotificationCenter *)notificationCenter NS_DESIGNATED_INITIALIZER;
+- (instancetype)initWithPhoto:(nullable id <NYTPhoto>)photo itemIndex:(NSUInteger)itemIndex loadingView:(nullable UIView *)loadingView notificationCenter:(nullable NSNotificationCenter *)notificationCenter NS_DESIGNATED_INITIALIZER;
 
 @end
 
diff --git a/NYTPhotoViewer/NYTPhotoViewController.m b/NYTPhotoViewer/NYTPhotoViewController.m
index 301854c9..50755d32 100644
--- a/NYTPhotoViewer/NYTPhotoViewController.m
+++ b/NYTPhotoViewer/NYTPhotoViewController.m
@@ -18,7 +18,9 @@
 
 @interface NYTPhotoViewController () <UIScrollViewDelegate>
 
-@property (nonatomic) id <NYTPhoto> photo;
+@property (nonatomic, nullable) id <NYTPhoto> photo;
+@property (nonatomic, nullable) UIView *interstitialView;
+@property (nonatomic) NSUInteger photoViewItemIndex;
 
 - (instancetype)initWithCoder:(NSCoder *)aDecoder NS_DESIGNATED_INITIALIZER;
 
@@ -43,14 +45,14 @@ - (void)dealloc {
 #pragma mark - UIViewController
 
 - (instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
-    return [self initWithPhoto:nil loadingView:nil notificationCenter:nil];
+    return [self initWithPhoto:nil itemIndex:0 loadingView:nil notificationCenter:nil];
 }
 
 - (instancetype)initWithCoder:(NSCoder *)aDecoder {
     self = [super initWithCoder:aDecoder];
 
     if (self) {
-        [self commonInitWithPhoto:nil loadingView:nil notificationCenter:nil];
+        [self commonInitWithPhoto:nil itemIndex:0 loadingView:nil notificationCenter:nil];
     }
 
     return self;
@@ -86,18 +88,20 @@ - (BOOL)prefersHomeIndicatorAutoHidden {
 
 #pragma mark - NYTPhotoViewController
 
-- (instancetype)initWithPhoto:(id <NYTPhoto>)photo loadingView:(UIView *)loadingView notificationCenter:(NSNotificationCenter *)notificationCenter {
+- (instancetype)initWithPhoto:(id <NYTPhoto>)photo itemIndex:(NSUInteger)itemIndex loadingView:(UIView *)loadingView notificationCenter:(NSNotificationCenter *)notificationCenter {
     self = [super initWithNibName:nil bundle:nil];
     
     if (self) {
-        [self commonInitWithPhoto:photo loadingView:loadingView notificationCenter:notificationCenter];
+        [self commonInitWithPhoto:photo itemIndex:itemIndex loadingView:loadingView notificationCenter:notificationCenter];
     }
     
     return self;
 }
 
-- (void)commonInitWithPhoto:(id <NYTPhoto>)photo loadingView:(UIView *)loadingView notificationCenter:(NSNotificationCenter *)notificationCenter {
+- (void)commonInitWithPhoto:(id <NYTPhoto>)photo itemIndex:(NSUInteger)itemIndex loadingView:(UIView *)loadingView notificationCenter:(NSNotificationCenter *)notificationCenter {
     _photo = photo;
+    _interstitialView = nil;
+    _photoViewItemIndex = itemIndex;
     
     if (photo.imageData) {
         _scalingImageView = [[NYTScalingImageView alloc] initWithImageData:photo.imageData frame:CGRectZero];
diff --git a/NYTPhotoViewer/NYTPhotoViewer.h b/NYTPhotoViewer/NYTPhotoViewer.h
index c28f4983..1d601a51 100644
--- a/NYTPhotoViewer/NYTPhotoViewer.h
+++ b/NYTPhotoViewer/NYTPhotoViewer.h
@@ -29,7 +29,7 @@ FOUNDATION_EXPORT const unsigned char NYTPhotoViewerVersionString[];
 // Protocols
 #import <NYTPhotoViewer/NYTPhoto.h>
 #import <NYTPhotoViewer/NYTPhotoCaptionViewLayoutWidthHinting.h>
-#import <NYTPhotoViewer/NYTPhotoContainer.h>
+#import <NYTPhotoViewer/NYTPhotoViewerContainer.h>
 #import <NYTPhotoViewer/NYTPhotoViewerDataSource.h>
 
 // Support
diff --git a/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.h b/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.h
index f1a6baf2..1295441e 100644
--- a/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.h
+++ b/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.h
@@ -14,6 +14,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 /**
  *  A simple concrete implementation of `NYTPhotoViewerDataSource`, for use with an array of images.
+ *  Does not support interstitial views.
  */
 @interface NYTPhotoViewerArrayDataSource : NSObject <NYTPhotoViewerDataSource, NSFastEnumeration>
 
diff --git a/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.m b/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.m
index 37d8ea53..562a34ae 100644
--- a/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.m
+++ b/NYTPhotoViewer/NYTPhotoViewerArrayDataSource.m
@@ -63,7 +63,7 @@ - (NSInteger)indexOfPhoto:(id <NYTPhoto>)photo {
 #pragma mark - Subscripting
 
 - (id<NYTPhoto>)objectAtIndexedSubscript:(NSUInteger)idx {
-    return self.photos[idx];
+    return [self photoAtIndex:idx];
 }
 
 @end
diff --git a/NYTPhotoViewer/NYTPhotoViewerCore.h b/NYTPhotoViewer/NYTPhotoViewerCore.h
index 55dc8a38..e25cfb8a 100644
--- a/NYTPhotoViewer/NYTPhotoViewerCore.h
+++ b/NYTPhotoViewer/NYTPhotoViewerCore.h
@@ -29,7 +29,7 @@ FOUNDATION_EXPORT const unsigned char NYTPhotoViewerCoreVersionString[];
 // Protocols
 #import <NYTPhotoViewer/NYTPhoto.h>
 #import <NYTPhotoViewer/NYTPhotoCaptionViewLayoutWidthHinting.h>
-#import <NYTPhotoViewer/NYTPhotoContainer.h>
+#import <NYTPhotoViewer/NYTPhotoViewerContainer.h>
 #import <NYTPhotoViewer/NYTPhotoViewerDataSource.h>
 
 // Support
diff --git a/NYTPhotoViewer/NYTPhotosViewController.h b/NYTPhotoViewer/NYTPhotosViewController.h
index be8a9845..d1cafcc7 100644
--- a/NYTPhotoViewer/NYTPhotosViewController.h
+++ b/NYTPhotoViewer/NYTPhotosViewController.h
@@ -23,6 +23,8 @@ NS_ASSUME_NONNULL_BEGIN
  */
 extern NSString * const NYTPhotosViewControllerDidNavigateToPhotoNotification;
 
+extern NSString * const NYTPhotosViewControllerDidNavigateToInterstitialViewNotification;
+
 /**
  *  Notification name issued when this `NYTPhotosViewController` is about to be dismissed.
  *
@@ -184,6 +186,15 @@ extern NSString * const NYTPhotosViewControllerDidDismissNotification;
  */
 - (void)photosViewController:(NYTPhotosViewController *)photosViewController didNavigateToPhoto:(id <NYTPhoto>)photo atIndex:(NSUInteger)photoIndex;
 
+/**
+ *  Called when a new interstitial view is displayed through a swipe gesture.
+ *
+ *  @param photosViewController The `NYTPhotosViewController` instance that sent the delegate message.
+ *  @param view                 The view that was just displayed.
+ *  @param index                The index of the view that was just displayed.
+ */
+- (void)photosViewController:(NYTPhotosViewController *)photosViewController didNavigateToInterstialView:(UIView *)view atIndex:(NSUInteger)index;
+
 /**
  *  Called immediately before the `NYTPhotosViewController` is about to start a user-initiated dismissal.
  *  This will be the beginning of the interactive panning to dismiss, if it is enabled and performed.
@@ -298,6 +309,16 @@ extern NSString * const NYTPhotosViewControllerDidDismissNotification;
  */
 - (void)photosViewController:(NYTPhotosViewController *)photosViewController actionCompletedWithActivityType:(NSString * _Nullable)activityType;
 
+/**
+ *  called when an `NYTInterstitialViewController` is created but before it is displayed. Returns the view to display as an interstitial view.
+ *
+ *  @param photosViewController The `NYTPhotosViewController` instance that sent the delegate message.
+ *  @param index                The index in the page view controller where the view will be displayed.
+ *
+ *  @return A `UIView`.
+ */
+- (UIView *)photosViewController:(NYTPhotosViewController *)photosViewController interstitialViewAtIndex:(NSUInteger)index;
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/NYTPhotoViewer/NYTPhotosViewController.m b/NYTPhotoViewer/NYTPhotosViewController.m
index 79e3281b..e089d081 100644
--- a/NYTPhotoViewer/NYTPhotosViewController.m
+++ b/NYTPhotoViewer/NYTPhotosViewController.m
@@ -10,6 +10,7 @@
 #import "NYTPhotoViewerDataSource.h"
 #import "NYTPhotoViewerArrayDataSource.h"
 #import "NYTPhotoViewController.h"
+#import "NYTInterstitialViewController.h"
 #import "NYTPhotoTransitionController.h"
 #import "NYTScalingImageView.h"
 #import "NYTPhoto.h"
@@ -22,6 +23,7 @@
 #endif
 
 NSString * const NYTPhotosViewControllerDidNavigateToPhotoNotification = @"NYTPhotosViewControllerDidNavigateToPhotoNotification";
+NSString * const NYTPhotosViewControllerDidNavigateToInterstitialViewNotification = @"NYTPhotosViewControllerDidNavigateToInterstitialViewNotification";
 NSString * const NYTPhotosViewControllerWillDismissNotification = @"NYTPhotosViewControllerWillDismissNotification";
 NSString * const NYTPhotosViewControllerDidDismissNotification = @"NYTPhotosViewControllerDidDismissNotification";
 
@@ -214,11 +216,12 @@ - (void)commonInitWithDataSource:(id <NYTPhotoViewerDataSource>)dataSource initi
 - (void)configurePageViewControllerWithInitialPhoto {
     NYTPhotoViewController *initialPhotoViewController;
 
-    if (self.initialPhoto != nil && [self.dataSource indexOfPhoto:self.initialPhoto] != NSNotFound) {
-        initialPhotoViewController = [self newPhotoViewControllerForPhoto:self.initialPhoto];
+    NSInteger initialPhotoIndex = [self.dataSource indexOfPhoto:self.initialPhoto];
+    if (self.initialPhoto != nil && initialPhotoIndex != NSNotFound) {
+        initialPhotoViewController = [self newPhotoViewControllerForPhoto:self.initialPhoto atIndex:initialPhotoIndex];
     }
     else {
-        initialPhotoViewController = [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:0]];
+        initialPhotoViewController = [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:0] atIndex:0];
     }
 
     [self setCurrentlyDisplayedViewController:initialPhotoViewController animated:NO];
@@ -239,7 +242,7 @@ - (void)addOverlayView {
 
 - (void)updateOverlayInformation {
     NSString *overlayTitle;
-    NSUInteger photoIndex = [self.dataSource indexOfPhoto:self.currentlyDisplayedPhoto];
+    NSUInteger photoIndex = self.currentPhotoViewController.photoViewItemIndex;
     NSInteger displayIndex = photoIndex + 1;
     
     if ([self.delegate respondsToSelector:@selector(photosViewController:titleForPhoto:atIndex:totalPhotoCount:)]) {
@@ -249,9 +252,10 @@ - (void)updateOverlayInformation {
     if (!overlayTitle && self.dataSource.numberOfPhotos == nil) {
         overlayTitle = [NSString localizedStringWithFormat:@"%lu", (unsigned long)displayIndex];
     }
-    
-    if (!overlayTitle && self.dataSource.numberOfPhotos.integerValue > 1) {
-        overlayTitle = [NSString localizedStringWithFormat:NSLocalizedString(@"%lu of %lu", nil), (unsigned long)displayIndex, (unsigned long)self.dataSource.numberOfPhotos.integerValue];
+
+    NSInteger totalItems = [self totalItemCount];
+    if (!overlayTitle && totalItems > 1) {
+        overlayTitle = [NSString localizedStringWithFormat:NSLocalizedString(@"%lu of %lu", nil), (unsigned long)displayIndex, (unsigned long)totalItems];
     }
     
     self.overlayView.title = overlayTitle;
@@ -343,11 +347,12 @@ - (void)setRightBarButtonItems:(NSArray *)rightBarButtonItems {
 }
 
 - (void)displayPhoto:(id <NYTPhoto>)photo animated:(BOOL)animated {
-    if ([self.dataSource indexOfPhoto:photo] == NSNotFound) {
+    NSInteger indexOfPhoto = [self.dataSource indexOfPhoto:photo];
+    if (indexOfPhoto == NSNotFound) {
         return;
     }
     
-    NYTPhotoViewController *photoViewController = [self newPhotoViewControllerForPhoto:photo];
+    NYTPhotoViewController *photoViewController = [self newPhotoViewControllerForPhoto:photo atIndex:indexOfPhoto];
     [self setCurrentlyDisplayedViewController:photoViewController animated:animated];
     [self updateOverlayInformation];
 }
@@ -458,7 +463,7 @@ - (void)dismissViewControllerAnimated:(BOOL)animated userInitiated:(BOOL)isUserI
 
 #pragma mark - Convenience
 
-- (void)setCurrentlyDisplayedViewController:(UIViewController <NYTPhotoContainer> *)viewController animated:(BOOL)animated {
+- (void)setCurrentlyDisplayedViewController:(UIViewController <NYTPhotoViewerContainer> *)viewController animated:(BOOL)animated {
     if (!viewController) {
         return;
     }
@@ -467,8 +472,8 @@ - (void)setCurrentlyDisplayedViewController:(UIViewController <NYTPhotoContainer
         animated = NO;
     }
 
-    NSInteger currentIdx = [self.dataSource indexOfPhoto:self.currentlyDisplayedPhoto];
-    NSInteger newIdx = [self.dataSource indexOfPhoto:viewController.photo];
+    NSInteger currentIdx = self.currentPhotoViewController.photoViewItemIndex;
+    NSInteger newIdx = viewController.photoViewItemIndex;
     UIPageViewControllerNavigationDirection direction = (newIdx < currentIdx) ? UIPageViewControllerNavigationDirectionReverse : UIPageViewControllerNavigationDirectionForward;
     
     [self.pageViewController setViewControllers:@[viewController] direction:direction animated:animated completion:nil];
@@ -496,14 +501,14 @@ - (void)setOverlayViewHidden:(BOOL)hidden animated:(BOOL)animated {
     }
 }
 
-- (NYTPhotoViewController *)newPhotoViewControllerForPhoto:(id <NYTPhoto>)photo {
+- (NYTPhotoViewController *)newPhotoViewControllerForPhoto:(id <NYTPhoto>)photo atIndex:(NSUInteger)index {
     if (photo) {
         UIView *loadingView;
         if ([self.delegate respondsToSelector:@selector(photosViewController:loadingViewForPhoto:)]) {
             loadingView = [self.delegate photosViewController:self loadingViewForPhoto:photo];
         }
         
-        NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:photo loadingView:loadingView notificationCenter:self.notificationCenter];
+        NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:photo itemIndex:index loadingView:loadingView notificationCenter:self.notificationCenter];
         photoViewController.delegate = self;
         [self.singleTapGestureRecognizer requireGestureRecognizerToFail:photoViewController.doubleTapGestureRecognizer];
 
@@ -518,14 +523,34 @@ - (NYTPhotoViewController *)newPhotoViewControllerForPhoto:(id <NYTPhoto>)photo
     return nil;
 }
 
-- (void)didNavigateToPhoto:(id <NYTPhoto>)photo {
+- (UIViewController *)newViewControllerAtIndex:(NSUInteger)index {
+    if ([self.delegate respondsToSelector:@selector(photosViewController:interstitialViewAtIndex:)]) {
+        UIView *view = [self.delegate photosViewController:self interstitialViewAtIndex:index];
+
+        NYTInterstitialViewController *interstitialViewController = [[NYTInterstitialViewController alloc] initWithView:view itemIndex:index];
+
+        return interstitialViewController;
+    }
+
+    return nil;
+}
+
+- (void)didNavigateToPhoto:(id <NYTPhoto>)photo atIndex:(NSUInteger)index {
     if ([self.delegate respondsToSelector:@selector(photosViewController:didNavigateToPhoto:atIndex:)]) {
-        [self.delegate photosViewController:self didNavigateToPhoto:photo atIndex:[self.dataSource indexOfPhoto:photo]];
+        [self.delegate photosViewController:self didNavigateToPhoto:photo atIndex:index];
     }
     
     [[NSNotificationCenter defaultCenter] postNotificationName:NYTPhotosViewControllerDidNavigateToPhotoNotification object:self];
 }
 
+- (void)didNavigateToInterstitialView:(UIView *)view atIndex:(NSUInteger)index {
+    if ([self.delegate respondsToSelector:@selector(photosViewController:didNavigateToInterstialView:atIndex:)]) {
+        [self.delegate photosViewController:self didNavigateToInterstialView:view atIndex:index];
+    }
+
+    [[NSNotificationCenter defaultCenter] postNotificationName:NYTPhotosViewControllerDidNavigateToInterstitialViewNotification object:self];
+}
+
 - (id <NYTPhoto>)currentlyDisplayedPhoto {
     return self.currentPhotoViewController.photo;
 }
@@ -546,6 +571,14 @@ - (CGPoint)boundsCenterPoint {
     return CGPointMake(CGRectGetMidX(self.view.bounds), CGRectGetMidY(self.view.bounds));
 }
 
+- (NSInteger)totalItemCount {
+    NSInteger numberOfInterstitialViews = 0;
+    if ([self.dataSource respondsToSelector:@selector(numberOfInterstitialViews)]) {
+        numberOfInterstitialViews = self.dataSource.numberOfInterstitialViews.integerValue;
+    }
+    return self.dataSource.numberOfPhotos.integerValue + numberOfInterstitialViews;
+}
+
 #pragma mark - NYTPhotoViewControllerDelegate
 
 - (void)photoViewController:(NYTPhotoViewController *)photoViewController didLongPressWithGestureRecognizer:(UILongPressGestureRecognizer *)longPressGestureRecognizer {
@@ -569,22 +602,40 @@ - (void)photoViewController:(NYTPhotoViewController *)photoViewController didLon
 
 #pragma mark - UIPageViewControllerDataSource
 
-- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController <NYTPhotoContainer> *)viewController {
-    NSUInteger photoIndex = [self.dataSource indexOfPhoto:viewController.photo];
-    if (photoIndex == 0 || photoIndex == NSNotFound) {
+- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerBeforeViewController:(UIViewController <NYTPhotoViewerContainer> *)viewController {
+    NSUInteger itemIndex = viewController.photoViewItemIndex;
+    if (itemIndex == 0) {
         return nil;
     }
 
-    return [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:(photoIndex - 1)]];
+    NSUInteger beforeIndex = itemIndex - 1;
+    BOOL isPhotoAvailableAtIndex = true;
+    if ([self.dataSource respondsToSelector:@selector(isPhotoAtIndex:)]) {
+        isPhotoAvailableAtIndex = [self.dataSource isPhotoAtIndex:beforeIndex];
+    }
+    if (isPhotoAvailableAtIndex) {
+        return [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:beforeIndex] atIndex:beforeIndex];
+    } else {
+        return [self newViewControllerAtIndex:beforeIndex];
+    }
 }
 
-- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController <NYTPhotoContainer> *)viewController {
-    NSUInteger photoIndex = [self.dataSource indexOfPhoto:viewController.photo];
-    if (photoIndex == NSNotFound) {
+- (UIViewController *)pageViewController:(UIPageViewController *)pageViewController viewControllerAfterViewController:(UIViewController <NYTPhotoViewerContainer> *)viewController {
+    NSUInteger itemIndex = viewController.photoViewItemIndex;
+    NSUInteger afterIndex = itemIndex + 1;
+    if (afterIndex >= [self totalItemCount]) {
         return nil;
     }
 
-    return [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:(photoIndex + 1)]];
+    BOOL isPhotoAvailableAtIndex = true;
+    if ([self.dataSource respondsToSelector:@selector(isPhotoAtIndex:)]) {
+        isPhotoAvailableAtIndex = [self.dataSource isPhotoAtIndex:afterIndex];
+    }
+    if (isPhotoAvailableAtIndex) {
+        return [self newPhotoViewControllerForPhoto:[self.dataSource photoAtIndex:afterIndex] atIndex:afterIndex];
+    } else {
+        return [self newViewControllerAtIndex:afterIndex];
+    }
 }
 
 #pragma mark - UIPageViewControllerDelegate
@@ -592,9 +643,13 @@ - (UIViewController *)pageViewController:(UIPageViewController *)pageViewControl
 - (void)pageViewController:(UIPageViewController *)pageViewController didFinishAnimating:(BOOL)finished previousViewControllers:(NSArray *)previousViewControllers transitionCompleted:(BOOL)completed {
     if (completed) {
         [self updateOverlayInformation];
-        
-        UIViewController <NYTPhotoContainer> *photoViewController = pageViewController.viewControllers.firstObject;
-        [self didNavigateToPhoto:photoViewController.photo];
+
+        UIViewController <NYTPhotoViewerContainer> *viewController = pageViewController.viewControllers.firstObject;
+        if (viewController.photo == nil) {
+            [self didNavigateToInterstitialView:viewController.interstitialView atIndex:viewController.photoViewItemIndex];
+        } else {
+            [self didNavigateToPhoto:viewController.photo atIndex:viewController.photoViewItemIndex];
+        }
     }
 }
 
diff --git a/NYTPhotoViewer/Protocols/NYTPhotoContainer.h b/NYTPhotoViewer/Protocols/NYTPhotoContainer.h
deleted file mode 100644
index ca9bd1f7..00000000
--- a/NYTPhotoViewer/Protocols/NYTPhotoContainer.h
+++ /dev/null
@@ -1,21 +0,0 @@
-//
-//  NYTPhotoContainer.h
-//  NYTPhotoViewer
-//
-//  Created by Brian Capps on 2/11/15.
-//
-//
-
-@protocol NYTPhoto;
-
-/**
- *  A protocol that defines that an object contains a photo property.
- */
-@protocol NYTPhotoContainer <NSObject>
-
-/**
- *  An object conforming to the `NYTPhoto` protocol.
- */
-@property (nonatomic, readonly) id <NYTPhoto> photo;
-
-@end
diff --git a/NYTPhotoViewer/Protocols/NYTPhotoViewerContainer.h b/NYTPhotoViewer/Protocols/NYTPhotoViewerContainer.h
new file mode 100644
index 00000000..907070f7
--- /dev/null
+++ b/NYTPhotoViewer/Protocols/NYTPhotoViewerContainer.h
@@ -0,0 +1,35 @@
+//
+//  NYTPhotoViewerContainer.h
+//  NYTPhotoViewer
+//
+//  Created by Brian Capps on 2/11/15.
+//
+//
+
+@protocol NYTPhoto;
+
+/**
+ *  A protocol that defines that an object contains a photo or interstitial view property
+ *  and the index of the item in the collection.
+ */
+@protocol NYTPhotoViewerContainer <NSObject>
+
+/**
+ *  An object conforming to the `NYTPhoto` protocol.
+ *  Will be nil if the container has a view.
+ */
+@property (nonatomic, readonly, nullable) id <NYTPhoto> photo;
+
+/**
+ *  A view to be displayed instead of a photo.
+ *  Will be nil if the container has a photo.
+ */
+@property (nonatomic, readonly, nullable) UIView *interstitialView;
+
+/**
+ *  The index of this item in the collection.
+ */
+
+@property (nonatomic, readonly) NSUInteger photoViewItemIndex;
+
+@end
diff --git a/NYTPhotoViewer/Protocols/NYTPhotoViewerDataSource.h b/NYTPhotoViewer/Protocols/NYTPhotoViewerDataSource.h
index 6f6ad5b5..4d1d4d9b 100644
--- a/NYTPhotoViewer/Protocols/NYTPhotoViewerDataSource.h
+++ b/NYTPhotoViewer/Protocols/NYTPhotoViewerDataSource.h
@@ -19,7 +19,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  *  Alternatively, `NYTPhotoViewerArrayDataSource` and `NYTPhotoViewerSinglePhotoDataSource` are concrete classes which conveniently handle the most common use cases for NYTPhotoViewer.
  */
-@protocol NYTPhotoViewerDataSource
+@protocol NYTPhotoViewerDataSource <NSObject>
 
 /**
  *  The total number of photos in the data source, or `nil` if the number is not known.
@@ -46,6 +46,31 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (nullable id <NYTPhoto>)photoAtIndex:(NSInteger)photoIndex;
 
+@optional
+
+/**
+ *  The total number of interstitial views in the data source.
+ *
+ *  The number returned should package an `NSInteger` value.
+ *
+ *  @return The number of interstitial views or `nil` if the number is not known.
+ */
+- (NSNumber *)numberOfInterstitialViews;
+
+/**
+ *  Indicates if the item at the specified index is a photo.
+ *
+ *  @return `true` if the item at the specified index is a photo, `false` otherwise.
+ */
+- (BOOL)isPhotoAtIndex:(NSInteger)idx;
+
+/**
+ *  Indicates if the item at the specified index is an interstitial view.
+ *
+ *  @return `true` if the item at the specified index is an interstitial view, `false` otherwise.
+ */
+- (BOOL)isInterstitialViewAtIndex:(NSInteger)idx;
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/NYTPhotoViewerTests/NYTPhotoViewControllerTests.m b/NYTPhotoViewerTests/NYTPhotoViewControllerTests.m
index c5fa61a1..9373f717 100644
--- a/NYTPhotoViewerTests/NYTPhotoViewControllerTests.m
+++ b/NYTPhotoViewerTests/NYTPhotoViewControllerTests.m
@@ -19,34 +19,34 @@ @interface NYTPhotoViewControllerTests : XCTestCase
 @implementation NYTPhotoViewControllerTests
 
 - (void)testScalingImageViewExistsAferInitialization {
-    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] loadingView:nil notificationCenter:nil];
+    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] itemIndex:0 loadingView:nil notificationCenter:nil];
     XCTAssertNotNil(photoViewController.scalingImageView);
 }
 
 - (void)testDoubleTapGestureRecognizerExistsAferInitialization {
-    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] loadingView:nil notificationCenter:nil];
+    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] itemIndex:0 loadingView:nil notificationCenter:nil];
     XCTAssertNotNil(photoViewController.doubleTapGestureRecognizer);
 }
 
 - (void)testLoadingViewExistsAferNilInitialization {
-    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] loadingView:nil notificationCenter:nil];
+    NYTPhotoViewController *photoViewController = [[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] itemIndex:0 loadingView:nil notificationCenter:nil];
     XCTAssertNotNil(photoViewController.loadingView);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForPhotoArgument {
-    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:nil loadingView:[[UIView alloc] init] notificationCenter:[NSNotificationCenter defaultCenter]]);
+    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:nil itemIndex:0 loadingView:[[UIView alloc] init] notificationCenter:[NSNotificationCenter defaultCenter]]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForLoadingViewArgument {
-    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] loadingView:nil notificationCenter:[NSNotificationCenter defaultCenter]]);
+    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] itemIndex:0 loadingView:nil notificationCenter:[NSNotificationCenter defaultCenter]]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForNotificationCenterArgument {
-    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] loadingView:[[UIView alloc] init] notificationCenter:nil]);
+    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:[self newTestPhoto] itemIndex:0 loadingView:[[UIView alloc] init] notificationCenter:nil]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForAllArguments {
-    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:nil loadingView:nil notificationCenter:nil]);
+    XCTAssertNoThrow([[NYTPhotoViewController alloc] initWithPhoto:nil itemIndex:0 loadingView:nil notificationCenter:nil]);
 }
 
 - (NYTExamplePhoto *)newTestPhoto {
diff --git a/NYTPhotoViewerTests/NYTPhotosDataSourceTests.m b/NYTPhotoViewerTests/NYTPhotoViewerArrayDataSourceTests.m
similarity index 56%
rename from NYTPhotoViewerTests/NYTPhotosDataSourceTests.m
rename to NYTPhotoViewerTests/NYTPhotoViewerArrayDataSourceTests.m
index af688cb9..f6f91593 100644
--- a/NYTPhotoViewerTests/NYTPhotosDataSourceTests.m
+++ b/NYTPhotoViewerTests/NYTPhotoViewerArrayDataSourceTests.m
@@ -9,37 +9,37 @@
 @import UIKit;
 @import XCTest;
 
-#import <NYTPhotoViewer/NYTPhotosDataSource.h>
 #import "NYTExamplePhoto.h"
+#import "NYTPhotoViewerArrayDataSource.h"
 
-@interface NYTPhotosDataSourceTests : XCTestCase
+@interface NYTPhotoViewerArrayDataSourceTests : XCTestCase
 
 @end
 
-@implementation NYTPhotosDataSourceTests
+@implementation NYTPhotoViewerArrayDataSourceTests
 
 - (void)testInitializerAcceptsNil {
-    XCTAssertNoThrow([[NYTPhotosDataSource alloc] initWithPhotos:nil]);
+    XCTAssertNoThrow([[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:nil]);
 }
 
 - (void)testOutOfBoundsDoesNotCrash {
-    NYTPhotosDataSource *dataSource = [[NYTPhotosDataSource alloc] initWithPhotos:nil];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:nil];
     XCTAssertNoThrow(dataSource[1]);
 }
 
 - (void)testOutOfBoundsReturnsNil {
-    NYTPhotosDataSource *dataSource = [[NYTPhotosDataSource alloc] initWithPhotos:nil];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:nil];
     XCTAssertNil(dataSource[1]);
 }
 
 - (void)testValidIndexReturnsPhoto {
-    NYTPhotosDataSource *dataSource = [[NYTPhotosDataSource alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:[self newTestPhotos]];
     XCTAssertNotNil(dataSource[1]);
 }
 
 - (void)testValidIndexReturnsCorrectPhoto {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosDataSource *dataSource = [[NYTPhotosDataSource alloc] initWithPhotos:photos];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:photos];
     XCTAssertEqualObjects(photos.firstObject, dataSource[0]);
 }
 
diff --git a/NYTPhotoViewerTests/NYTPhotoViewerSinglePhotoDataSourceTests.m b/NYTPhotoViewerTests/NYTPhotoViewerSinglePhotoDataSourceTests.m
new file mode 100644
index 00000000..cf00330b
--- /dev/null
+++ b/NYTPhotoViewerTests/NYTPhotoViewerSinglePhotoDataSourceTests.m
@@ -0,0 +1,64 @@
+//
+//  NYTPhotosDataSourceTests.m
+//  NYTPhotoViewer
+//
+//  Created by Brian Capps on 2/26/15.
+//  Copyright (c) 2015 NYTimes. All rights reserved.
+//
+
+@import UIKit;
+@import XCTest;
+
+#import "NYTExamplePhoto.h"
+#import "NYTPhotoViewerSinglePhotoDataSource.h"
+
+@interface NYTPhotoViewerSinglePhotoDataSourceTests : XCTestCase
+
+@end
+
+@implementation NYTPhotoViewerSinglePhotoDataSourceTests
+
+- (void)testInitializerAcceptsNil {
+    XCTAssertNoThrow([[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:nil]);
+}
+
+- (void)testOutOfBoundsDoesNotCrash {
+    NYTPhotoViewerSinglePhotoDataSource *dataSource = [[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:nil];
+    XCTAssertNoThrow([dataSource photoAtIndex:1]);
+}
+
+- (void)testOutOfBoundsReturnsNil {
+    NYTPhotoViewerSinglePhotoDataSource *dataSource = [[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:nil];
+    XCTAssertNil([dataSource photoAtIndex:1]);
+}
+
+- (void)testValidIndexReturnsPhotoAtIndex {
+    NYTExamplePhoto *photo = [[NYTExamplePhoto alloc] init];
+    NYTPhotoViewerSinglePhotoDataSource *dataSource = [[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:photo];
+    XCTAssertEqual(0, [dataSource indexOfPhoto:photo]);
+}
+
+- (void)testValidIndexReturnsPhoto {
+    NYTExamplePhoto *photo = [[NYTExamplePhoto alloc] init];
+    NYTPhotoViewerSinglePhotoDataSource *dataSource = [[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:photo];
+    XCTAssertNotNil([dataSource photoAtIndex:1]);
+}
+
+- (void)testValidIndexReturnsCorrectPhoto {
+    NSArray *photos = [self newTestPhotos];
+    NYTPhotoViewerSinglePhotoDataSource *dataSource = [[NYTPhotoViewerSinglePhotoDataSource alloc] initWithPhoto:photos.firstObject];
+    XCTAssertEqualObjects(photos.firstObject, [dataSource photoAtIndex:0]);
+}
+
+- (NSArray *)newTestPhotos {
+    NSMutableArray *photos = [NSMutableArray array];
+    
+    for (int i = 0; i < 5; i++) {
+        NYTExamplePhoto *photo = [[NYTExamplePhoto alloc] init];
+        [photos addObject:photo];
+    }
+    
+    return photos;
+}
+
+@end
diff --git a/NYTPhotoViewerTests/NYTPhotosViewControllerTests.m b/NYTPhotoViewerTests/NYTPhotosViewControllerTests.m
index 93d01452..14be0d31 100644
--- a/NYTPhotoViewerTests/NYTPhotosViewControllerTests.m
+++ b/NYTPhotoViewerTests/NYTPhotosViewControllerTests.m
@@ -13,6 +13,8 @@
 
 #import <NYTPhotoViewer/NYTPhotosViewController.h>
 #import "NYTExamplePhoto.h"
+#import "NYTPhotoViewerArrayDataSource.h"
+
 
 @interface NYTPhotosViewControllerTests : XCTestCase
 @end
@@ -28,56 +30,62 @@ - (void)doneButtonTapped:(id)sender;
 @implementation NYTPhotosViewControllerTests
 
 - (void)testPanGestureRecognizerExistsAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.panGestureRecognizer);
 }
 
 - (void)testPanGestureRecognizerHasAssociatedViewAfterViewDidLoad {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     __unused id view = photosViewController.view;
     XCTAssertNotNil(photosViewController.panGestureRecognizer.view);
 }
 
 - (void)testSingleTapGestureRecognizerExistsAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.singleTapGestureRecognizer);
 }
 
 - (void)testSingleTapGestureRecognizerHasAssociatedViewAfterViewDidLoad {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     __unused id view = photosViewController.view;
     XCTAssertNotNil(photosViewController.singleTapGestureRecognizer.view);
 }
 
 - (void)testPageViewControllerExistsAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     [photosViewController viewDidLoad];
-    
+
     XCTAssertNotNil(photosViewController.pageViewController);
 }
 
 - (void)testPageViewControllerDoesNotHaveAssociatedSuperviewBeforeViewLoads {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNil(photosViewController.pageViewController.view.superview);
 }
 
 - (void)testPageViewControllerHasAssociatedSuperviewAfterViewLoads {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     photosViewController.view = photosViewController.view; // Referencing the view loads it.
     XCTAssertNotNil(photosViewController.pageViewController.view.superview);
 }
 
 - (void)testCurrentlyDisplayedPhotoIsFirstAfterConvenienceInitialization {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+
+     NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:photos];
+
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:dataSource];
     [photosViewController viewDidLoad];
 
     XCTAssertEqualObjects(photos.firstObject, photosViewController.currentlyDisplayedPhoto);
 }
 
+
 - (void)testCurrentlyDisplayedPhotoIsAccurateAfterSettingInitialPhoto {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.lastObject];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:photos];
+
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:dataSource initialPhoto:photos.lastObject delegate:nil];
     [photosViewController viewDidLoad];
 
     XCTAssertEqualObjects(photos.lastObject, photosViewController.currentlyDisplayedPhoto);
@@ -85,7 +93,9 @@ - (void)testCurrentlyDisplayedPhotoIsAccurateAfterSettingInitialPhoto {
 
 - (void)testCurrentlyDisplayedPhotoIsAccurateAfterDisplayPhotoCall {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.lastObject];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:photos];
+
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:dataSource initialPhoto:photos.lastObject delegate:nil];
     [photosViewController viewDidLoad];
     [photosViewController displayPhoto:photos.firstObject animated:NO];
 
@@ -93,162 +103,161 @@ - (void)testCurrentlyDisplayedPhotoIsAccurateAfterDisplayPhotoCall {
 }
 
 - (void)testLeftBarButtonItemIsPopulatedAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.leftBarButtonItem);
 }
 
 - (void)testLeftBarButtonItemIsNilAfterSettingToNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     photosViewController.leftBarButtonItem = nil;
     XCTAssertNil(photosViewController.leftBarButtonItem);
 }
 
 - (void)testLeftBarButtonItemsArePopulatedAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.leftBarButtonItems);
 }
 
 - (void)testLeftBarButtonItemsAreNilAfterSettingToNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     photosViewController.leftBarButtonItems = nil;
     XCTAssertNil(photosViewController.leftBarButtonItems);
 }
 
 - (void)testRightBarButtonItemIsPopulatedAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.rightBarButtonItem);
 }
 
 - (void)testRightBarButtonItemIsNilAfterSettingToNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     photosViewController.rightBarButtonItem = nil;
     XCTAssertNil(photosViewController.rightBarButtonItem);
 }
 
 - (void)testRightBarButtonItemsArePopulatedAfterInitialization {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNotNil(photosViewController.rightBarButtonItems);
 }
 
 - (void)testRightBarButtonItemsAreNilAfterSettingToNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     photosViewController.rightBarButtonItems = nil;
     XCTAssertNil(photosViewController.rightBarButtonItems);
 }
 
 - (void)testOneArgConvenienceInitializerAcceptsNil {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:nil]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:nil]);
 }
 
 - (void)testTwoArgConvenienceInitializerAcceptsNilForPhotosParameter {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:nil initialPhoto:[[NYTExamplePhoto alloc] init]]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:nil initialPhoto:[[NYTExamplePhoto alloc] init] delegate:nil]);
 }
 
 - (void)testTwoArgConvenienceInitializerAcceptsNilForInitialPhotoParameter {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos] initialPhoto:nil]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:nil delegate:nil]);
 }
 
 - (void)testTwoArgConvenienceInitializerAcceptsNilForBothParameters {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:nil initialPhoto:nil]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:nil initialPhoto:nil delegate:nil]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForPhotosParameter {
     id delegateMock = OCMProtocolMock(@protocol(NYTPhotosViewControllerDelegate));
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:nil initialPhoto:[NYTExamplePhoto new] delegate:delegateMock]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:nil initialPhoto:[NYTExamplePhoto new] delegate:delegateMock]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForInitialPhotoParameter {
     id delegateMock = OCMProtocolMock(@protocol(NYTPhotosViewControllerDelegate));
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos] initialPhoto:nil delegate:delegateMock]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:nil delegate:delegateMock]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForDelegateParameter {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos] initialPhoto:[NYTExamplePhoto new] delegate:nil]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:[NYTExamplePhoto new] delegate:nil]);
 }
 
 - (void)testDesignatedInitializerAcceptsNilForAllParameters {
-    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithPhotos:nil initialPhoto:nil delegate:nil]);
+    XCTAssertNoThrow([[NYTPhotosViewController alloc] initWithDataSource:nil initialPhoto:nil delegate:nil]);
 }
 
 - (void)testDesignatedInitializerSetsDelegate {
     id delegateMock = OCMProtocolMock(@protocol(NYTPhotosViewControllerDelegate));
-    NYTPhotosViewController *sut = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos] initialPhoto:nil delegate:delegateMock];
+    NYTPhotosViewController *sut = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:nil delegate:delegateMock];
 
     XCTAssertEqual(sut.delegate, delegateMock);
 }
 
 - (void)testDisplayPhotoAcceptsNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
     XCTAssertNoThrow([photosViewController displayPhoto:nil animated:NO]);
 }
 
 - (void)testDisplayPhotoDoesNothingWhenPassedPhotoOutsideDataSource {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.firstObject];
+    NYTPhotoViewerArrayDataSource *dataSource = [[NYTPhotoViewerArrayDataSource alloc] initWithPhotos:photos];
+
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:dataSource initialPhoto:photos.firstObject delegate:nil];
     [photosViewController viewDidLoad];
-    
+
     NYTExamplePhoto *invalidPhoto = [[NYTExamplePhoto alloc] init];
-    
+
     [photosViewController displayPhoto:invalidPhoto animated:NO];
     XCTAssertEqualObjects(photos.firstObject, photosViewController.currentlyDisplayedPhoto);
 }
 
 - (void)testDisplayPhotoMovesToCorrectPhoto {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.firstObject];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:photos.firstObject delegate:nil];
     [photosViewController viewDidLoad];
 
     NYTExamplePhoto *photoToDisplay = photos[2];
-    
+
     [photosViewController displayPhoto:photoToDisplay animated:NO];
     XCTAssertEqualObjects(photoToDisplay, photosViewController.currentlyDisplayedPhoto);
 }
 
 - (void)testUpdateImageForPhotoAcceptsNil {
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:[self newTestPhotos]];
-    XCTAssertNoThrow([photosViewController updateImageForPhoto:nil]);
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
+    XCTAssertNoThrow([photosViewController updatePhoto:nil]);
 }
 
 - (void)testUpdateImageForPhotoDoesNothingWhenPassedPhotoOutsideDataSource {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.firstObject];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:photos.firstObject delegate:nil];
     NYTExamplePhoto *invalidPhoto = [[NYTExamplePhoto alloc] init];
     invalidPhoto.image = [[UIImage alloc] init];
-    
-    [photosViewController updateImageForPhoto:invalidPhoto];
-    
+
+    [photosViewController updatePhoto:invalidPhoto];
+
     XCTAssertEqualObjects(photosViewController.currentlyDisplayedPhoto.image, [photos.firstObject image]);
 }
 
 - (void)testUpdateImageForPhotoUpdatesImage {
     NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos initialPhoto:photos.firstObject];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource] initialPhoto:photos.firstObject delegate:nil];
 
     NYTExamplePhoto *photoToUpdate = photos.firstObject;
     photoToUpdate.image = [UIImage imageNamed:@"NYTimesBuilding" inBundle:[NSBundle bundleForClass:[self class]] compatibleWithTraitCollection:nil];
-    
-    [photosViewController updateImageForPhoto:photoToUpdate];
-    
+
+    [photosViewController updatePhoto:photoToUpdate];
+
     XCTAssertEqualObjects(photosViewController.currentlyDisplayedPhoto.image, photoToUpdate.image);
 }
 
 - (void)testViewIsntLoadedAfterInit {
-    NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
 
     XCTAssertFalse(photosViewController.isViewLoaded);
 }
 
 - (void)testPageViewIsntLoadedAfterInit {
-    NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
 
     XCTAssertFalse(photosViewController.pageViewController.isViewLoaded);
 }
 
 - (void)testDoneButtonDismissalUserInitiatedFlagIsTrue {
-    NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
 
     id photosVCMock = OCMPartialMock(photosViewController);
 
@@ -258,8 +267,7 @@ - (void)testDoneButtonDismissalUserInitiatedFlagIsTrue {
 }
 
 - (void)testGestureBasedDismissalUserInitiatedFlagIsTrue {
-    NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
 
     id photosVCMock = OCMPartialMock(photosViewController);
 
@@ -272,8 +280,7 @@ - (void)testGestureBasedDismissalUserInitiatedFlagIsTrue {
 }
 
 - (void)testProgrammaticDismissalUserInitiatedFlagIsFalse {
-    NSArray *photos = [self newTestPhotos];
-    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithPhotos:photos];
+    NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc] initWithDataSource:[self newTestPhotosDataSource]];
 
     id photosVCMock = OCMPartialMock(photosViewController);
 
@@ -295,4 +302,10 @@ - (NSArray *)newTestPhotos {
     return photos;
 }
 
+- (NYTPhotoViewerArrayDataSource *)newTestPhotosDataSource {
+
+    return [NYTPhotoViewerArrayDataSource dataSourceWithPhotos:[self newTestPhotos]];
+
+}
+
 @end
diff --git a/README.md b/README.md
index 3e8a4116..dcf4727e 100644
--- a/README.md
+++ b/README.md
@@ -19,7 +19,7 @@ NYTPhotosViewController *photosViewController = [[NYTPhotosViewController alloc]
 
 ## Running the Example
 
-The Example project uses [Carthage](https://github.com/Carthage/Carthage) to integrate its dependencies. If you don’t have Carthge installed, you can install it via [Homebrew](http://brew.sh) with `brew install carthage`.
+The Example project uses [Carthage](https://github.com/Carthage/Carthage) to integrate its dependencies. If you don’t have Carthage installed, you can install it via [Homebrew](http://brew.sh) with `brew install carthage`.
 
 Then, in your checkout of the `NYTPhotoViewer` repo, run `carthage checkout --use-submodules`.