diff --git a/src/Main.elm b/src/Main.elm
index 64e8c30..7420373 100644
--- a/src/Main.elm
+++ b/src/Main.elm
@@ -71,9 +71,13 @@ updateLoginResponse model r = case r of
     Err e  -> (model, Cmd.none)
 
 updateSyncResponse : Model -> Result Http.Error SyncResponse -> (Model, Cmd Msg)
-updateSyncResponse model r = let sync = model.sync in case r of
-    Ok sr -> ({ model | sync = mergeSyncResponse model.sync sr }, Cmd.none)
-    _ -> (model, Cmd.none)
+updateSyncResponse model r =
+    let
+        cmd = sync model.sync.nextBatch model.apiUrl <| Maybe.withDefault "" model.token
+    in
+        case r of
+            Ok sr -> ({ model | sync = mergeSyncResponse model.sync sr }, cmd)
+            _ -> (model, cmd)
 
 subscriptions : Model -> Sub Msg
 subscriptions m = Sub.none
diff --git a/src/Scylla/Http.elm b/src/Scylla/Http.elm
index 113e335..b2ac6a3 100644
--- a/src/Scylla/Http.elm
+++ b/src/Scylla/Http.elm
@@ -3,8 +3,8 @@ import Scylla.Model exposing (..)
 import Scylla.Api exposing (..)
 import Scylla.Sync exposing (syncResponseDecoder)
 import Scylla.Login exposing (loginResponseDecoder, Username, Password)
-import Json.Encode exposing (object, string)
-import Http exposing (request, jsonBody, expectJson)
+import Json.Encode exposing (object, string, int)
+import Http exposing (request, emptyBody, jsonBody, expectJson)
 
 fullUrl : ApiUrl -> ApiUrl
 fullUrl s = s ++ "/_matrix/client/r0"
@@ -15,7 +15,18 @@ firstSync apiUrl token = request
     { method = "GET"
     , headers = authenticatedHeaders token
     , url = (fullUrl apiUrl) ++ "/sync"
-    , body = jsonBody <| object []
+    , body = emptyBody
+    , expect = expectJson ReceiveSyncResponse syncResponseDecoder
+    , timeout = Nothing
+    , tracker = Nothing
+    }
+
+sync : String -> ApiUrl -> ApiToken -> Cmd Msg
+sync nextBatch apiUrl token = request
+    { method = "GET"
+    , headers = authenticatedHeaders token
+    , url = (fullUrl apiUrl) ++ "/sync" ++ "?since=" ++ (nextBatch) ++ "&timeout=10000"
+    , body = emptyBody
     , expect = expectJson ReceiveSyncResponse syncResponseDecoder
     , timeout = Nothing
     , tracker = Nothing
diff --git a/src/Scylla/Sync.elm b/src/Scylla/Sync.elm
index 5346055..6217df2 100644
--- a/src/Scylla/Sync.elm
+++ b/src/Scylla/Sync.elm
@@ -3,6 +3,7 @@ import Scylla.Api exposing (..)
 import Dict exposing (Dict)
 import Json.Decode as Decode exposing (Decoder, int, string, float, list, value, dict, bool, field)
 import Json.Decode.Pipeline exposing (required, optional)
+import Set exposing (Set)
 
 -- Special Decoding
 decodeJust : Decoder a -> Decoder (Maybe a)
@@ -256,8 +257,95 @@ presenceDecoder =
         |> maybeDecode "events" (list eventDecoder)
 
 -- Business Logic
+uniqueByRecursive : (a -> comparable) -> List a -> Set comparable -> List a
+uniqueByRecursive f l s = case l of
+    x::tail -> if Set.member (f x) s
+        then uniqueByRecursive f tail s
+        else x::uniqueByRecursive f tail (Set.insert (f x) s)
+    [] -> []
+
+uniqueBy : (a -> comparable) -> List a -> List a
+uniqueBy f l = uniqueByRecursive f l Set.empty
+
+mergeMaybe : (a -> a -> a) -> Maybe a -> Maybe a -> Maybe a
+mergeMaybe f l r = case (l, r) of
+    (Just v1, Just v2) -> Just <| f v1 v2
+    (Just v, Nothing) -> Just v
+    (Nothing, Just v) -> Just v
+    _ -> Nothing
+
+mergeEvents : List Event -> List Event -> List Event
+mergeEvents l1 l2 = l1 ++ l2
+
+mergeStateEvents : List StateEvent -> List StateEvent -> List StateEvent
+mergeStateEvents l1 l2 = l1 ++ l2
+
+mergeRoomEvents : List RoomEvent -> List RoomEvent -> List RoomEvent
+mergeRoomEvents l1 l2 = l1 ++ l2
+
+mergeStrippedStates : List StrippedState -> List StrippedState -> List StrippedState
+mergeStrippedStates l1 l2 = l1 ++ l2
+
+mergeAccountData : AccountData -> AccountData -> AccountData
+mergeAccountData a1 a2 = AccountData <| mergeMaybe mergeEvents a1.events a2.events
+
+mergePresence : Presence -> Presence -> Presence
+mergePresence p1 p2 = Presence <| mergeMaybe mergeEvents p1.events p2.events
+
+mergeDicts : (b -> b -> b) -> Dict comparable b -> Dict comparable b -> Dict comparable b
+mergeDicts f d1 d2 =
+    let
+        inOne = Dict.insert
+        inBoth k v1 v2 = Dict.insert k (f v1 v2)
+    in
+        Dict.merge inOne inBoth inOne d1 d2 (Dict.empty)
+
+mergeState : State -> State -> State
+mergeState s1 s2 = State <| mergeMaybe mergeStateEvents s1.events s2.events
+
+mergeTimeline : Timeline -> Timeline -> Timeline
+mergeTimeline t1 t2 = Timeline (mergeMaybe mergeRoomEvents t1.events t2.events) Nothing t2.prevBatch
+
+mergeJoinedRoom : JoinedRoom -> JoinedRoom -> JoinedRoom
+mergeJoinedRoom r1 r2 =
+    { r2 | state = mergeMaybe mergeState r1.state r2.state
+    , timeline = mergeMaybe mergeTimeline r1.timeline r2.timeline
+    , accountData = mergeMaybe mergeAccountData r1.accountData r2.accountData
+    }
+
+mergeInviteState : InviteState -> InviteState -> InviteState 
+mergeInviteState i1 i2 = InviteState <| mergeMaybe mergeStrippedStates i1.events i2.events
+
+mergeInvitedRoom : InvitedRoom -> InvitedRoom -> InvitedRoom
+mergeInvitedRoom i1 i2 = InvitedRoom <| mergeMaybe mergeInviteState i1.inviteState i2.inviteState
+
+mergeLeftRoom : LeftRoom -> LeftRoom -> LeftRoom
+mergeLeftRoom l1 l2 = LeftRoom
+    (mergeMaybe mergeState l1.state l2.state)
+    (mergeMaybe mergeTimeline l1.timeline l2.timeline)
+    (mergeMaybe mergeAccountData l1.accountData l2.accountData)
+
+mergeJoin : Dict String JoinedRoom -> Dict String JoinedRoom -> Dict String JoinedRoom
+mergeJoin = mergeDicts mergeJoinedRoom
+
+mergeInvite : Dict String InvitedRoom -> Dict String InvitedRoom -> Dict String InvitedRoom
+mergeInvite = mergeDicts mergeInvitedRoom
+
+mergeLeave : Dict String LeftRoom -> Dict String LeftRoom -> Dict String LeftRoom
+mergeLeave = mergeDicts mergeLeftRoom
+
+mergeRooms : Rooms -> Rooms -> Rooms
+mergeRooms r1 r2 =
+    { join = mergeMaybe mergeJoin r1.join r2.join
+    , invite = mergeMaybe mergeInvite r1.invite r2.invite
+    , leave = mergeMaybe mergeLeave r1.leave r2.leave
+    }
+
 mergeSyncResponse : SyncResponse -> SyncResponse -> SyncResponse
-mergeSyncResponse l r = r
+mergeSyncResponse l r =
+    { r | rooms = mergeMaybe mergeRooms l.rooms r.rooms
+    , accountData = mergeMaybe mergeAccountData l.accountData r.accountData
+    }
 
 roomName : JoinedRoom -> Maybe String
 roomName jr =