diff --git a/Libraries/ActionSheetIOS/ActionSheetIOS.js b/Libraries/ActionSheetIOS/ActionSheetIOS.js
index b84fedf0c..20150d6f6 100644
--- a/Libraries/ActionSheetIOS/ActionSheetIOS.js
+++ b/Libraries/ActionSheetIOS/ActionSheetIOS.js
@@ -7,6 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule ActionSheetIOS
+ * @flow
  */
 'use strict';
 
@@ -15,7 +16,7 @@ var RCTActionSheetManager = require('NativeModules').ActionSheetManager;
 var invariant = require('invariant');
 
 var ActionSheetIOS = {
-  showActionSheetWithOptions(options, callback) {
+  showActionSheetWithOptions(options: Object, callback: Function) {
     invariant(
       typeof options === 'object' && options !== null,
       'Options must a valid object'
@@ -31,7 +32,11 @@ var ActionSheetIOS = {
     );
   },
 
-  showShareActionSheetWithOptions(options, failureCallback, successCallback) {
+  showShareActionSheetWithOptions(
+    options: Object,
+    failureCallback: Function,
+    successCallback: Function
+  ) {
     invariant(
       typeof options === 'object' && options !== null,
       'Options must a valid object'
diff --git a/Libraries/AdSupport/AdSupportIOS.js b/Libraries/AdSupport/AdSupportIOS.js
index 0f2a4c2a6..d9d315a1d 100644
--- a/Libraries/AdSupport/AdSupportIOS.js
+++ b/Libraries/AdSupport/AdSupportIOS.js
@@ -7,17 +7,18 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule AdSupportIOS
+ * @flow
  */
 'use strict';
 
 var AdSupport = require('NativeModules').AdSupport;
 
 module.exports = {
-  getAdvertisingId: function(onSuccess, onFailure) {
+  getAdvertisingId: function(onSuccess: Function, onFailure: Function) {
     AdSupport.getAdvertisingId(onSuccess, onFailure);
   },
 
-  getAdvertisingTrackingEnabled: function(onSuccess, onFailure) {
+  getAdvertisingTrackingEnabled: function(onSuccess: Function, onFailure: Function) {
     AdSupport.getAdvertisingTrackingEnabled(onSuccess, onFailure);
   },
 };
diff --git a/Libraries/Animation/LayoutAnimation.js b/Libraries/Animation/LayoutAnimation.js
index 8752e2322..b68656984 100644
--- a/Libraries/Animation/LayoutAnimation.js
+++ b/Libraries/Animation/LayoutAnimation.js
@@ -7,6 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule LayoutAnimation
+ * @flow
  */
 'use strict';
 
@@ -42,6 +43,15 @@ var animChecker = createStrictShapeTypeChecker({
   ),
 });
 
+type Anim = {
+  duration?: number;
+  delay?: number;
+  springDamping?: number;
+  initialVelocity?: number;
+  type?: $Enum<typeof Types>;
+  property?: $Enum<typeof Properties>;
+}
+
 var configChecker = createStrictShapeTypeChecker({
   duration: PropTypes.number.isRequired,
   create: animChecker,
@@ -49,46 +59,56 @@ var configChecker = createStrictShapeTypeChecker({
   delete: animChecker,
 });
 
-var LayoutAnimation = {
-  configureNext(config, onAnimationDidEnd, onError) {
-    configChecker({config}, 'config', 'LayoutAnimation.configureNext');
-    RCTUIManager.configureNextLayoutAnimation(config, onAnimationDidEnd, onError);
-  },
-  create(duration, type, creationProp) {
-    return {
-      duration,
-      create: {
-        type,
-        property: creationProp,
-      },
-      update: {
-        type,
-      },
-    };
-  },
-  Types: Types,
-  Properties: Properties,
-  configChecker: configChecker,
-};
+type Config = {
+  duration: number;
+  create?: Anim;
+  update?: Anim;
+  delete?: Anim;
+}
 
-LayoutAnimation.Presets = {
-  easeInEaseOut: LayoutAnimation.create(
-    0.3, Types.easeInEaseOut, Properties.opacity
-  ),
-  linear: LayoutAnimation.create(
-    0.5, Types.linear, Properties.opacity
-  ),
-  spring: {
-    duration: 0.7,
+function configureNext(config: Config, onAnimationDidEnd?: Function, onError?: Function) {
+  configChecker({config}, 'config', 'LayoutAnimation.configureNext');
+  RCTUIManager.configureNextLayoutAnimation(config, onAnimationDidEnd, onError);
+}
+
+function create(duration: number, type, creationProp): Config {
+  return {
+    duration,
     create: {
-      type: Types.linear,
-      property: Properties.opacity,
+      type,
+      property: creationProp,
     },
     update: {
-      type: Types.spring,
-      springDamping: 0.4,
+      type,
     },
-  },
+  };
+}
+
+var LayoutAnimation = {
+  configureNext,
+  create,
+  Types,
+  Properties,
+  configChecker: configChecker,
+  Presets: {
+    easeInEaseOut: create(
+      0.3, Types.easeInEaseOut, Properties.opacity
+    ),
+    linear: create(
+      0.5, Types.linear, Properties.opacity
+    ),
+    spring: {
+      duration: 0.7,
+      create: {
+        type: Types.linear,
+        property: Properties.opacity,
+      },
+      update: {
+        type: Types.spring,
+        springDamping: 0.4,
+      },
+    },
+  }
 };
 
 module.exports = LayoutAnimation;
diff --git a/Libraries/AppRegistry/AppRegistry.js b/Libraries/AppRegistry/AppRegistry.js
index 40498adac..f36f88132 100644
--- a/Libraries/AppRegistry/AppRegistry.js
+++ b/Libraries/AppRegistry/AppRegistry.js
@@ -7,6 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule AppRegistry
+ * @flow
  */
 'use strict';
 
@@ -21,6 +22,12 @@ if (__DEV__) {
 
 var runnables = {};
 
+type AppConfig = {
+  appKey: string;
+  component: ReactClass<any, any, any>;
+  run?: Function;
+};
+
 /**
  * `AppRegistry` is the JS entry point to running all React Native apps.  App
  * root components should register themselves with
@@ -33,17 +40,18 @@ var runnables = {};
  * `require`d.
  */
 var AppRegistry = {
-  registerConfig: function(config) {
+  registerConfig: function(config: Array<AppConfig>) {
     for (var i = 0; i < config.length; ++i) {
-      if (config[i].run) {
-        AppRegistry.registerRunnable(config[i].appKey, config[i].run);
+      var appConfig = config[i];
+      if (appConfig.run) {
+        AppRegistry.registerRunnable(appConfig.appKey, appConfig.run);
       } else {
-        AppRegistry.registerComponent(config[i].appKey, config[i].component);
+        AppRegistry.registerComponent(appConfig.appKey, appConfig.component);
       }
     }
   },
 
-  registerComponent: function(appKey, getComponentFunc) {
+  registerComponent: function(appKey: string, getComponentFunc: Function): string {
     runnables[appKey] = {
       run: (appParameters) =>
         renderApplication(getComponentFunc(), appParameters.initialProps, appParameters.rootTag)
@@ -51,12 +59,12 @@ var AppRegistry = {
     return appKey;
   },
 
-  registerRunnable: function(appKey, func) {
+  registerRunnable: function(appKey: string, func: Function): string {
     runnables[appKey] = {run: func};
     return appKey;
   },
 
-  runApplication: function(appKey, appParameters) {
+  runApplication: function(appKey: string, appParameters: any): void {
     console.log(
       'Running application "' + appKey + '" with appParams: ' +
       JSON.stringify(appParameters) + '. ' +
diff --git a/Libraries/AppStateIOS/AppStateIOS.android.js b/Libraries/AppStateIOS/AppStateIOS.android.js
index 9fbad761e..b8c3e8def 100644
--- a/Libraries/AppStateIOS/AppStateIOS.android.js
+++ b/Libraries/AppStateIOS/AppStateIOS.android.js
@@ -7,6 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule AppStateIOS
+ * @flow
  */
 'use strict';
 
diff --git a/Libraries/AppStateIOS/AppStateIOS.ios.js b/Libraries/AppStateIOS/AppStateIOS.ios.js
index ecb2ee49e..af6893534 100644
--- a/Libraries/AppStateIOS/AppStateIOS.ios.js
+++ b/Libraries/AppStateIOS/AppStateIOS.ios.js
@@ -7,6 +7,7 @@
  * of patent rights can be found in the PATENTS file in the same directory.
  *
  * @providesModule AppStateIOS
+ * @flow
  */
 'use strict';