diff --git a/4_Shop_App/App.js b/4_Shop_App/App.js
index b47ca82..2bc2a60 100644
--- a/4_Shop_App/App.js
+++ b/4_Shop_App/App.js
@@ -1,15 +1,14 @@
-import React, { useState } from 'react';
-import { createStore, combineReducers, applyMiddleware } from 'redux';
-import { Provider } from 'react-redux';
 import { AppLoading } from 'expo';
 import * as Font from 'expo-font';
+import React, { useState } from 'react';
+import { Provider } from 'react-redux';
+import { applyMiddleware, combineReducers, createStore } from 'redux';
 import ReduxThunk from 'redux-thunk';
-
-import productsReducer from './store/reducers/products';
+import NavigationContainer from './navigation/NavigationContainer';
+import authReducer from './store/reducers/auth';
 import cartReducer from './store/reducers/cart';
 import ordersReducer from './store/reducers/orders';
-import authReducer from './store/reducers/auth';
-import ShopNavigator from './navigation/ShopNavigator';
+import productsReducer from './store/reducers/products';
 
 const rootReducer = combineReducers({
     products: productsReducer,
@@ -43,7 +42,7 @@ export default function App() {
 
     return (
         <Provider store={store}>
-            <ShopNavigator />
+            <NavigationContainer />
         </Provider>
     );
 }
diff --git a/4_Shop_App/README.md b/4_Shop_App/README.md
index d641e2d..48ea7cb 100644
--- a/4_Shop_App/README.md
+++ b/4_Shop_App/README.md
@@ -22,6 +22,7 @@
     -   [When The App Launches](#whenapplaunches)
         -   [Authentication Screen](#authscreen)
     -   [Auth Config](#actionauth)
+-   [Local Storage - AsyncStorage](#localstorage)
 
 <h1 id='shopapp'>Shop App</h1>
 
@@ -905,3 +906,69 @@
 
             export default authReducer;
         ```
+
+<h1 id='localstorage'>Local Storage - AsyncStorage</h1>
+
+[Go Back to Summary](#summary)
+
+-   In `store/actions/auth.js`
+
+    -   Import **AsyncStorage** from `react-native`
+        -   `removeItem('key')` to remove key/value from local storage
+        -   `setItem('key', 'value')` to add key/value pair in the local storage
+            -   It has to be a string, so we have to JSON.stringify()
+        -   `getItem('key')` to get an item from local storage
+
+    ```JavaScript
+      import { AsyncStorage } from 'react-native';
+      import { FIREBASE_KEY } from 'react-native-dotenv';
+      export const AUTHENTICATE = 'AUTHENTICATE';
+      export const LOGOUT = 'LOGOUT';
+      let timer;
+
+      export const authenticate = (userId, token, expiryTime) => {
+          return (dispatch) => {
+              dispatch(setLogoutTimer(expiryTime));
+              dispatch({ type: AUTHENTICATE, userId, token });
+          };
+      };
+
+      export const signup = (email, password) => {
+          return async (dispatch) => {...};
+      };
+
+      export const login = (email, password) => {
+          return async (dispatch) => {...};
+      };
+
+      export const logout = () => {
+          clearLogoutTimer();
+          AsyncStorage.removeItem('userData');
+          return { type: LOGOUT };
+      };
+
+      const clearLogoutTimer = () => {
+          if (timer) {
+              clearTimeout(timer);
+          }
+      };
+
+      const setLogoutTimer = (expirationTime) => {
+          return (dispatch) => {
+              timer = setTimeout(() => {
+                  dispatch(logout());
+              }, expirationTime);
+          };
+      };
+
+      const saveDataToStorage = (token, userId, expirationDate) => {
+          AsyncStorage.setItem(
+              'userData',
+              JSON.stringify({
+                  token,
+                  userId,
+                  expiryDate: expirationDate.toISOString(),
+              }),
+          );
+      };
+    ```
diff --git a/4_Shop_App/navigation/NavigationContainer.js b/4_Shop_App/navigation/NavigationContainer.js
new file mode 100644
index 0000000..283fa77
--- /dev/null
+++ b/4_Shop_App/navigation/NavigationContainer.js
@@ -0,0 +1,19 @@
+import React, { useEffect, useRef } from 'react';
+import { NavigationActions } from 'react-navigation';
+import { useSelector } from 'react-redux';
+import ShopNavigator from './ShopNavigator';
+
+function NavigationContainer(props) {
+    const navRef = useRef();
+    const isAuth = useSelector((state) => !!state.auth.token);
+
+    useEffect(() => {
+        if (!isAuth) {
+            navRef.current.dispatch(NavigationActions.navigate({ routeName: 'Auth' }));
+        }
+    }, [isAuth]);
+
+    return <ShopNavigator ref={navRef} />;
+}
+
+export default NavigationContainer;
diff --git a/4_Shop_App/navigation/ShopNavigator.js b/4_Shop_App/navigation/ShopNavigator.js
index 8429059..573f999 100644
--- a/4_Shop_App/navigation/ShopNavigator.js
+++ b/4_Shop_App/navigation/ShopNavigator.js
@@ -1,19 +1,20 @@
+import { Ionicons } from '@expo/vector-icons';
 import React from 'react';
-import { createStackNavigator } from 'react-navigation-stack';
+import { Button, Platform, SafeAreaView, StyleSheet, View } from 'react-native';
 import { createAppContainer, createSwitchNavigator } from 'react-navigation';
-import { createDrawerNavigator } from 'react-navigation-drawer';
-import { Platform } from 'react-native';
-import { Ionicons } from '@expo/vector-icons';
-
+import { createDrawerNavigator, DrawerNavigatorItems } from 'react-navigation-drawer';
+import { createStackNavigator } from 'react-navigation-stack';
+import { useDispatch } from 'react-redux';
 import Colors from '../css/Colors';
-
-import ProductsOverviewScreen from '../screens/shop/ProductsOverviewScreen';
-import ProductDetailsScreen from '../screens/shop/ProductDetailsScreen';
 import CartScreen from '../screens/shop/CartScreen';
 import OrdersScreen from '../screens/shop/OrdersScreen';
-import UserProductsScreen from '../screens/user/UserProductsScreen';
-import EditProductScreen from '../screens/user/EditProductScreen';
+import ProductDetailsScreen from '../screens/shop/ProductDetailsScreen';
+import ProductsOverviewScreen from '../screens/shop/ProductsOverviewScreen';
+import StartupScreen from '../screens/StartupScreen';
 import AuthScreen from '../screens/user/AuthScreen';
+import EditProductScreen from '../screens/user/EditProductScreen';
+import UserProductsScreen from '../screens/user/UserProductsScreen';
+import * as authActions from '../store/actions/auth';
 
 const defaultNavOptions = {
     headerStyle: {
@@ -104,12 +105,38 @@ const ShopNavigator = createDrawerNavigator(
         contentOptions: {
             activeTintColor: Colors.primary,
         },
+        contentComponent: (props) => {
+            const dispatch = useDispatch();
+            return (
+                <View style={styles.drawerButton}>
+                    <SafeAreaView forceInset={{ top: 'always', horizontal: 'never' }}>
+                        <DrawerNavigatorItems {...props} />
+                        <Button
+                            title="Logout"
+                            color={Colors.primary}
+                            onPress={() => {
+                                dispatch(authActions.logout());
+                                // props.navigation.navigate('Auth');
+                            }}
+                        />
+                    </SafeAreaView>
+                </View>
+            );
+        },
     },
 );
 
 const MainNavigator = createSwitchNavigator({
+    Startup: StartupScreen,
     Auth: AuthNavigator,
     Shop: ShopNavigator,
 });
 
+const styles = StyleSheet.create({
+    drawerButton: {
+        flex: 1,
+        paddingTop: 20,
+    },
+});
+
 export default createAppContainer(MainNavigator);
diff --git a/4_Shop_App/screens/StartupScreen.js b/4_Shop_App/screens/StartupScreen.js
new file mode 100644
index 0000000..a5f1b30
--- /dev/null
+++ b/4_Shop_App/screens/StartupScreen.js
@@ -0,0 +1,52 @@
+import React, { useEffect } from 'react';
+import { ActivityIndicator, AsyncStorage, StyleSheet, View } from 'react-native';
+import { useDispatch } from 'react-redux';
+import Colors from '../css/Colors';
+import * as authActions from '../store/actions/auth';
+
+function StartupScreen({ navigation }) {
+    const dispatch = useDispatch();
+
+    useEffect(() => {
+        const tryLogin = async () => {
+            const userData = await AsyncStorage.getItem('userData');
+
+            if (!userData) {
+                navigation.navigate('Auth');
+                return;
+            }
+
+            const transformedData = JSON.parse(userData);
+            const { token, userId, expiryDate } = transformedData;
+            const expirationDate = new Date(expiryDate);
+
+            if (expirationDate <= new Date() || !token || !userId) {
+                navigation.navigate('Auth');
+                return;
+            }
+
+            const expirationTime = expirationDate.getTime() - new Date().getTime();
+
+            navigation.navigate('Shop');
+            dispatch(authActions.authenticate(userId, token, expirationTime));
+        };
+
+        tryLogin();
+    }, [dispatch]);
+
+    return (
+        <View style={styles.screen}>
+            <ActivityIndicator size="large" color={Colors.primary} />
+        </View>
+    );
+}
+
+const styles = StyleSheet.create({
+    screen: {
+        flex: 1,
+        justifyContent: 'center',
+        alignItems: 'center',
+    },
+});
+
+export default StartupScreen;
diff --git a/4_Shop_App/store/actions/auth.js b/4_Shop_App/store/actions/auth.js
index 7bcf2f8..24fe07d 100644
--- a/4_Shop_App/store/actions/auth.js
+++ b/4_Shop_App/store/actions/auth.js
@@ -1,6 +1,15 @@
+import { AsyncStorage } from 'react-native';
 import { FIREBASE_KEY } from 'react-native-dotenv';
-export const SIGNUP = 'SIGNUP';
-export const LOGIN = 'LOGIN';
+export const AUTHENTICATE = 'AUTHENTICATE';
+export const LOGOUT = 'LOGOUT';
+let timer;
+
+export const authenticate = (userId, token, expiryTime) => {
+    return (dispatch) => {
+        dispatch(setLogoutTimer(expiryTime));
+        dispatch({ type: AUTHENTICATE, userId, token });
+    };
+};
 
 export const signup = (email, password) => {
     return async (dispatch) => {
@@ -40,12 +49,9 @@ export const signup = (email, password) => {
             }
 
             const resData = await response.json();
-
-            dispatch({
-                type: SIGNUP,
-                token: resData.idToken,
-                userId: resData.localId,
-            });
+            dispatch(authenticate(resData.localId, resData.idToken, parseInt(resData.expiresIn) * 1000));
+            const expirationDate = new Date(new Date().getTime() + parseInt(resData.expiresIn) * 1000);
+            saveDataToStorage(resData.idToken, resData.localId, expirationDate);
         } catch (error) {
             throw error;
         }
@@ -93,13 +99,42 @@ export const login = (email, password) => {
             }
 
             const resData = await response.json();
-            dispatch({
-                type: LOGIN,
-                token: resData.idToken,
-                userId: resData.localId,
-            });
+            dispatch(authenticate(resData.localId, resData.idToken, parseInt(resData.expiresIn) * 1000));
+            const expirationDate = new Date(new Date().getTime() + parseInt(resData.expiresIn) * 1000);
+            saveDataToStorage(resData.idToken, resData.localId, expirationDate);
         } catch (error) {
             throw error;
         }
     };
 };
+
+export const logout = () => {
+    clearLogoutTimer();
+    AsyncStorage.removeItem('userData');
+    return { type: LOGOUT };
+};
+
+const clearLogoutTimer = () => {
+    if (timer) {
+        clearTimeout(timer);
+    }
+};
+
+const setLogoutTimer = (expirationTime) => {
+    return (dispatch) => {
+        timer = setTimeout(() => {
+            dispatch(logout());
+        }, expirationTime);
+    };
+};
+
+const saveDataToStorage = (token, userId, expirationDate) => {
+    AsyncStorage.setItem(
+        'userData',
+        JSON.stringify({
+            token,
+            userId,
+            expiryDate: expirationDate.toISOString(),
+        }),
+    );
+};
diff --git a/4_Shop_App/store/reducers/auth.js b/4_Shop_App/store/reducers/auth.js
index 4388025..a753548 100644
--- a/4_Shop_App/store/reducers/auth.js
+++ b/4_Shop_App/store/reducers/auth.js
@@ -1,4 +1,4 @@
-import { LOGIN, SIGNUP } from '../actions/auth';
+import { AUTHENTICATE, LOGOUT } from '../actions/auth';
 
 const initialState = {
     token: null,
@@ -7,16 +7,13 @@ const initialState = {
 
 const authReducer = (state = initialState, action) => {
     switch (action.type) {
-        case LOGIN:
-            return {
-                token: action.token,
-                userId: action.userId,
-            };
-        case SIGNUP:
+        case AUTHENTICATE:
             return {
                 token: action.token,
                 userId: action.userId,
             };
+        case LOGOUT:
+            return initialState;
         default:
             return state;
     }