diff --git a/package.json b/package.json
index 3d5db05..4ababd0 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@ezerous/drizzle",
-  "version": "0.1.0",
+  "version": "0.2.0",
   "description": "A reactive data-store for web3 and smart contracts.",
   "license": "MIT",
   "author": "Ezerous <ezerous@gmail.com>",
diff --git a/src/Drizzle.js b/src/Drizzle.js
index 02c50ec..b52eeed 100644
--- a/src/Drizzle.js
+++ b/src/Drizzle.js
@@ -6,7 +6,7 @@ import * as ContractActions from './contracts/constants'
 import * as DrizzleActions from './drizzleStatus/drizzleActions'
 
 // Load as promise so that async Drizzle initialization can still resolve
-var isEnvReadyPromise = new Promise((resolve, reject) => {
+const isEnvReadyPromise = new Promise((resolve) => {
   const hasNavigator = typeof navigator !== 'undefined'
   const hasWindow = typeof window !== 'undefined'
   const hasDocument = typeof document !== 'undefined'
@@ -81,12 +81,6 @@ class Drizzle {
       events
     )
 
-    if (this.contracts[drizzleContract.contractName]) {
-      throw new Error(
-        `Contract already exists: ${drizzleContract.contractName}`
-      )
-    }
-
     this.store.dispatch({ type: ContractActions.CONTRACT_INITIALIZING, contractConfig })
 
     this.contracts[drizzleContract.contractName] = drizzleContract
diff --git a/src/accountBalances/accountBalancesMiddleware.js b/src/accountBalances/accountBalancesMiddleware.js
index dcf3fc0..d784474 100644
--- a/src/accountBalances/accountBalancesMiddleware.js
+++ b/src/accountBalances/accountBalancesMiddleware.js
@@ -1,4 +1,4 @@
-import { WEB3_INITIALIZED } from '../web3/constants'
+import { WEB3_INITIALIZED } from '../web3/web3Actions'
 import { accountBalancesFetching } from './accountBalancesActions'
 import { ACCOUNTS_FETCHED } from '../accounts/accountsActions'
 
diff --git a/src/accountBalances/accountBalancesSaga.js b/src/accountBalances/accountBalancesSaga.js
index 6fa67ea..377e28c 100644
--- a/src/accountBalances/accountBalancesSaga.js
+++ b/src/accountBalances/accountBalancesSaga.js
@@ -1,7 +1,7 @@
 import { call, put, select, takeLatest } from 'redux-saga/effects'
 import {
-  ACCOUNT_BALANCES_FAILED,
   ACCOUNT_BALANCE_FETCHED,
+  ACCOUNT_BALANCES_FAILED,
   ACCOUNT_BALANCES_FETCHED,
   ACCOUNT_BALANCES_FETCHING
 } from './accountBalancesActions'
diff --git a/src/accounts/accountsMiddleware.js b/src/accounts/accountsMiddleware.js
index 73c3151..4c9128f 100644
--- a/src/accounts/accountsMiddleware.js
+++ b/src/accounts/accountsMiddleware.js
@@ -1,14 +1,14 @@
-import { WEB3_INITIALIZED } from '../web3/constants'
+import { WEB3_INITIALIZED } from '../web3/web3Actions'
 import { accountsFetched, accountsListening } from './accountsActions'
 
-export const accountsMiddleware = () => store => next => action => {
+export const accountsMiddleware = web3 => store => next => action => {
   const { type } = action
 
   if (type === WEB3_INITIALIZED) {
     if(!window.ethereum)
       console.warn('No Metamask detected, not subscribed to account changes!')
     else {
-      const { web3 } = action;
+      web3 = action.web3;
       window.ethereum.on('accountsChanged', accounts => {
         // For some reason accounts here are returned with lowercase letters, so we need to patch them
         let patchedAccounts = Array.from(accounts);
diff --git a/src/blocks/blocksSaga.js b/src/blocks/blocksSaga.js
index 8292263..091e7bc 100644
--- a/src/blocks/blocksSaga.js
+++ b/src/blocks/blocksSaga.js
@@ -1,5 +1,5 @@
 import { END, eventChannel } from 'redux-saga'
-import { call, put, take, takeEvery, takeLatest, all } from 'redux-saga/effects'
+import { all, call, put, take, takeEvery, takeLatest } from 'redux-saga/effects'
 import * as BlocksActions from './blockActions'
 
 /*
diff --git a/src/contractStateUtils.js b/src/contractStateUtils.js
index 8457648..6ed534a 100644
--- a/src/contractStateUtils.js
+++ b/src/contractStateUtils.js
@@ -22,6 +22,7 @@ export const generateContractInitialState = contractConfig => {
   return {
     initialized: false,
     synced: false,
+    deployed: true,
     ...objectOfConstants
   }
 }
diff --git a/src/contracts/constants.js b/src/contracts/constants.js
index c98ab27..54d4f54 100644
--- a/src/contracts/constants.js
+++ b/src/contracts/constants.js
@@ -4,6 +4,7 @@ export const EVENT_ERROR = 'EVENT_ERROR'
 export const LISTEN_FOR_EVENT = 'LISTEN_FOR_EVENT'
 export const CONTRACT_INITIALIZING = 'CONTRACT_INITIALIZING'
 export const CONTRACT_INITIALIZED = 'CONTRACT_INITIALIZED'
+export const CONTRACT_NOT_DEPLOYED = 'CONTRACT_NOT_DEPLOYED'
 export const GOT_CONTRACT_VAR = 'GOT_CONTRACT_VAR'
 export const DELETE_CONTRACT = 'DELETE_CONTRACT'
 export const CONTRACT_SYNCING = 'CONTRACT_SYNCING'
diff --git a/src/contracts/contractsReducer.js b/src/contracts/contractsReducer.js
index 8af3006..540ded4 100644
--- a/src/contracts/contractsReducer.js
+++ b/src/contracts/contractsReducer.js
@@ -29,6 +29,17 @@ const contractsReducer = (state = initialState, action) => {
     }
   }
 
+  // Contract not found on the current network
+  if (action.type === ContractActions.CONTRACT_NOT_DEPLOYED) {
+    return {
+      ...state,
+      [action.name]: {
+        ...state[action.name],
+        deployed: false
+      }
+    }
+  }
+
   if (action.type === ContractActions.DELETE_CONTRACT) {
     const { [action.contractName]: omitted, ...rest } = state
     return rest
diff --git a/src/contracts/contractsSaga.js b/src/contracts/contractsSaga.js
index 1ba4395..d50d342 100644
--- a/src/contracts/contractsSaga.js
+++ b/src/contracts/contractsSaga.js
@@ -199,7 +199,7 @@ function * callCallContractFn ({
   } catch (error) {
     console.error(error)
 
-    var errorArgs = {
+    const errorArgs = {
       name: contract.contractName,
       variable: contract.abi[fnIndex].name,
       argsHash: argsHash,
@@ -230,8 +230,8 @@ function * callSyncContract (action) {
   delete contractFnsState.events
 
   // Iterate over functions and hashes
-  for (var fnName in contractFnsState) {
-    for (var argsHash in contractFnsState[fnName]) {
+  for (let fnName in contractFnsState) {
+    for (let argsHash in contractFnsState[fnName]) {
       const fnIndex = contractFnsState[fnName][argsHash].fnIndex
       const args = contractFnsState[fnName][argsHash].args
 
@@ -271,6 +271,18 @@ function isSendOrCallOptions (options) {
   return false
 }
 
+export function * isContractDeployed ({ web3, contractConfig }) {
+  const networkId = yield call(web3.eth.net.getId);
+  if(contractConfig.networks[networkId]){
+    const contractAddress = contractConfig.networks[networkId].address;
+
+    const fetchedByteCode = yield call(web3.eth.getCode, contractAddress);
+    if(fetchedByteCode === contractConfig.deployedBytecode)
+      return true;
+  }
+  return false;
+}
+
 function * contractsSaga () {
   yield takeEvery(ContractActions.SEND_CONTRACT_TX, callSendContractTx)
   yield takeEvery(ContractActions.CALL_CONTRACT_FN, callCallContractFn)
diff --git a/src/drizzle-middleware.js b/src/drizzle-middleware.js
index 0718af2..71d96f4 100644
--- a/src/drizzle-middleware.js
+++ b/src/drizzle-middleware.js
@@ -1,6 +1,7 @@
 import * as DrizzleActions from './drizzleStatus/drizzleActions'
 import * as ContractActions from './contracts/constants'
 import { ACCOUNTS_FETCHED } from './accounts/accountsActions'
+import { NETWORK_ID_CHANGED } from './web3/web3Actions'
 
 export const drizzleMiddleware = drizzleInstance => store => next => action => {
   const { type } = action
@@ -9,6 +10,14 @@ export const drizzleMiddleware = drizzleInstance => store => next => action => {
     drizzleInstance = action.drizzle
   }
 
+  if (type === NETWORK_ID_CHANGED) {
+    store.dispatch({
+      type: DrizzleActions.DRIZZLE_INITIALIZING,
+      drizzle: drizzleInstance,
+      options: drizzleInstance.options
+    })
+  }
+
   if (
     type === ACCOUNTS_FETCHED &&
     drizzleInstance &&
diff --git a/src/drizzleStatus/drizzleStatusSaga.js b/src/drizzleStatus/drizzleStatusSaga.js
index db28571..7879f5e 100644
--- a/src/drizzleStatus/drizzleStatusSaga.js
+++ b/src/drizzleStatus/drizzleStatusSaga.js
@@ -1,13 +1,15 @@
 import { call, put, takeLatest } from 'redux-saga/effects'
 
 // Initialization Functions
-import { initializeWeb3, getNetworkId } from '../web3/web3Saga'
+import { getNetworkId, initializeWeb3 } from '../web3/web3Saga'
 import { getAccounts } from '../accounts/accountsSaga'
 import { getAccountBalances } from '../accountBalances/accountBalancesSaga'
 import * as DrizzleActions from './drizzleActions'
 import * as BlocksActions from '../blocks/blockActions'
 
-import { NETWORK_IDS, NETWORK_MISMATCH } from '../web3/constants'
+import { NETWORK_IDS, NETWORK_MISMATCH } from '../web3/web3Actions'
+import { CONTRACT_NOT_DEPLOYED } from '../contracts/constants'
+import { isContractDeployed } from '../contracts/contractsSaga'
 
 export function * initializeDrizzle (action) {
   try {
@@ -35,15 +37,19 @@ export function * initializeDrizzle (action) {
         yield call(getAccountBalances, { web3 })
 
         // Instantiate contracts passed through via options.
-        for (var i = 0; i < options.contracts.length; i++) {
-          var contractConfig = options.contracts[i]
-          var events = []
-          var contractName = contractConfig.contractName
-
+        for (let i = 0; i < options.contracts.length; i++) {
+          const contractConfig = options.contracts[i]
+          let events = []
+          const contractName = contractConfig.contractName;
           if (contractName in options.events) {
             events = options.events[contractName]
           }
 
+          if(!(yield call(isContractDeployed, { web3, contractConfig }))){
+            yield put({ type: CONTRACT_NOT_DEPLOYED, name: contractName })
+            throw `Contract ${contractName} not deployed on this network`
+          }
+
           yield call([drizzle, drizzle.addContract], contractConfig, events)
         }
 
diff --git a/src/generateStore.js b/src/generateStore.js
index 7d12a67..603b364 100644
--- a/src/generateStore.js
+++ b/src/generateStore.js
@@ -1,5 +1,5 @@
 import { all, fork } from 'redux-saga/effects'
-import { createStore, applyMiddleware, compose, combineReducers } from 'redux'
+import { applyMiddleware, combineReducers, compose, createStore } from 'redux'
 import createSagaMiddleware from 'redux-saga'
 import drizzleSagas from './rootSaga'
 import drizzleReducers from './reducer'
diff --git a/src/index.js b/src/index.js
index 83a3eb3..1f48a64 100644
--- a/src/index.js
+++ b/src/index.js
@@ -7,53 +7,27 @@ import * as EventActions from './contracts/constants'
 import * as AccountActions from './accounts/accountsActions'
 
 // Reducers
-import accountsReducer from './accounts/accountsReducer'
-import accountBalancesReducer from './accountBalances/accountBalancesReducer'
-import blocksReducer from './blocks/blocksReducer'
-import contractsReducer from './contracts/contractsReducer'
-import drizzleStatusReducer from './drizzleStatus/drizzleStatusReducer'
-import transactionsReducer from './transactions/transactionsReducer'
-import transactionStackReducer from './transactions/transactionStackReducer'
-import web3Reducer from './web3/web3Reducer'
+import drizzleReducers from './reducer'
 
 // Middleware
 import drizzleMiddleware from './drizzle-middleware'
 import accountsMiddleware from './accounts/accountsMiddleware'
 import accountBalancesMiddleware from './accountBalances/accountBalancesMiddleware'
+import web3Middleware from './web3/web3Middleware'
 
 // Sagas
-import accountBalancesSaga from './accountBalances/accountBalancesSaga'
-import blocksSaga from './blocks/blocksSaga'
-import contractsSaga from './contracts/contractsSaga'
-import drizzleStatusSaga from './drizzleStatus/drizzleStatusSaga'
-
-const drizzleReducers = {
-  accounts: accountsReducer,
-  accountBalances: accountBalancesReducer,
-  contracts: contractsReducer,
-  currentBlock: blocksReducer,
-  drizzleStatus: drizzleStatusReducer,
-  transactions: transactionsReducer,
-  transactionStack: transactionStackReducer,
-  web3: web3Reducer
-}
+import drizzleSagas from './rootSaga'
 
 const drizzleMiddlewares = [
   drizzleMiddleware,
   accountsMiddleware,
-  accountBalancesMiddleware
-]
-
-const drizzleSagas = [
-  accountBalancesSaga,
-  blocksSaga,
-  contractsSaga,
-  drizzleStatusSaga
+  accountBalancesMiddleware,
+  web3Middleware
 ]
 
 const drizzleActions = {
-  AccountActions,
-  EventActions
+  account: AccountActions,
+  event: EventActions
 }
 
 export {
diff --git a/src/mergeOptions.js b/src/mergeOptions.js
index f30bd87..10ddeae 100644
--- a/src/mergeOptions.js
+++ b/src/mergeOptions.js
@@ -1,5 +1,5 @@
 const merge = require('deepmerge');
-import isPlainObject from 'is-plain-object';
+import isPlainObject from 'is-plain-object'
 
 export default function (defaultOptions, newOptions) {
   return merge(defaultOptions, newOptions, {
diff --git a/src/web3/constants.js b/src/web3/web3Actions.js
similarity index 65%
rename from src/web3/constants.js
rename to src/web3/web3Actions.js
index 2943c92..2175bdc 100644
--- a/src/web3/constants.js
+++ b/src/web3/web3Actions.js
@@ -3,7 +3,9 @@ export const WEB3_INITIALIZED = 'WEB3_INITIALIZED'
 export const WEB3_FAILED = 'WEB3_FAILED'
 export const WEB3_USER_DENIED = 'WEB3_USER_DENIED'
 
+export const NETWORK_ID_FETCHING = 'NETWORK_ID_FETCHING'
 export const NETWORK_ID_FETCHED = 'NETWORK_ID_FETCHED'
+export const NETWORK_ID_CHANGED = 'NETWORK_ID_CHANGED'
 export const NETWORK_ID_FAILED = 'NETWORK_ID_FAILED'
 export const NETWORK_MISMATCH = 'NETWORK_MISMATCH'
 
@@ -15,3 +17,11 @@ export const NETWORK_IDS = {
     kovan: 42,
     ganache: 5777
 }
+
+export function networkIdChanged (web3, networkId) {
+    return {
+        type: NETWORK_ID_CHANGED,
+        web3,
+        networkId
+    }
+}
diff --git a/src/web3/web3Middleware.js b/src/web3/web3Middleware.js
new file mode 100644
index 0000000..2c4557c
--- /dev/null
+++ b/src/web3/web3Middleware.js
@@ -0,0 +1,23 @@
+import { networkIdChanged, WEB3_INITIALIZED } from './web3Actions'
+
+export const web3Middleware = web3 => store => next => action => {
+  const { type } = action
+
+  if (type === WEB3_INITIALIZED) {
+    if(!window.ethereum)
+      console.warn('No Metamask detected, not subscribed to network changes!')
+    else {
+      web3 = action.web3;
+      window.ethereum.on('networkChanged', (networkId) => {
+        // Warning: 'networkChanged' is deprecated (EIP-1193)
+        const storedNetworkId = store.getState().web3.networkId;
+        if(storedNetworkId && networkId !== storedNetworkId)
+          store.dispatch(networkIdChanged(web3, networkId));
+      });
+    }
+  }
+  return next(action)
+}
+
+const initializedMiddleware = web3Middleware(undefined)
+export default initializedMiddleware
diff --git a/src/web3/web3Reducer.js b/src/web3/web3Reducer.js
index e29677e..b81c50a 100644
--- a/src/web3/web3Reducer.js
+++ b/src/web3/web3Reducer.js
@@ -1,4 +1,4 @@
-import * as Action from './constants'
+import * as Action from './web3Actions'
 
 const initialState = {
   status: ''
@@ -33,7 +33,8 @@ const web3Reducer = (state = initialState, action) => {
     }
   }
 
-  if (action.type === Action.NETWORK_ID_FETCHED) {
+  if (action.type === Action.NETWORK_ID_FETCHED
+        || action.type === Action.NETWORK_ID_CHANGED) {
     return {
       ...state,
       networkId: action.networkId
diff --git a/src/web3/web3Saga.js b/src/web3/web3Saga.js
index cb13747..d3fc3ee 100644
--- a/src/web3/web3Saga.js
+++ b/src/web3/web3Saga.js
@@ -1,12 +1,11 @@
 import { call, put } from 'redux-saga/effects'
-import * as Action from './constants'
+import * as Action from './web3Actions'
 
 const Web3 = require('web3');
 
 /*
  * Initialization
  */
-
 export function * initializeWeb3 (options) {
   try {
     let web3 = {}
@@ -35,7 +34,6 @@ export function * initializeWeb3 (options) {
       } catch (error) {
         console.error(error)
         yield put({ type: Action.WEB3_FAILED })
-        return
       }
     } else if (typeof window.web3 !== 'undefined') {
       // Checking if Web3 has been injected by the browser (Mist/MetaMask)
@@ -71,20 +69,19 @@ export function * initializeWeb3 (options) {
 }
 
 /*
- * Network ID
+ * Fetch Network ID
  */
-
 export function * getNetworkId ({ web3 }) {
   try {
-    const networkId = yield call(web3.eth.net.getId)
+    const networkId = yield call(web3.eth.net.getId);
 
-    yield put({ type: Action.NETWORK_ID_FETCHED, networkId })
+    yield put({ type: Action.NETWORK_ID_FETCHED, networkId });
 
     return networkId
   } catch (error) {
-    yield put({ type: Action.NETWORK_ID_FAILED, error })
+    yield put({ type: Action.NETWORK_ID_FAILED, error });
 
-    console.error('Error fetching network ID:')
-    console.error(error)
+    console.error('Error fetching network ID:');
+    console.error(error);
   }
 }