diff --git a/elm.json b/elm.json
index 59e1a3e..cf69d5a 100644
--- a/elm.json
+++ b/elm.json
@@ -19,7 +19,8 @@
         "elm/http": "2.0.0 <= v < 3.0.0",
         "elm/json": "1.0.0 <= v < 2.0.0",
         "elm/time": "1.0.0 <= v < 2.0.0",
-        "elm/url": "1.0.0 <= v < 2.0.0"
+        "elm/url": "1.0.0 <= v < 2.0.0",
+        "miniBill/elm-fast-dict": "1.0.0 <= v < 2.0.0"
     },
     "test-dependencies": {}
 }
diff --git a/src/Internal/Tools/DefaultDict.elm b/src/Internal/Tools/DefaultDict.elm
new file mode 100644
index 0000000..13015e9
--- /dev/null
+++ b/src/Internal/Tools/DefaultDict.elm
@@ -0,0 +1,56 @@
+module Internal.Tools.DefaultDict exposing (..)
+
+import FastDict as Dict exposing (Dict)
+
+{-| A dictionary of keys and values that includes a default when a key doesn't exist.
+-}
+type DefaultDict k v
+    = DefaultDict
+        { content : Dict k v
+        , default : v
+        }
+
+{-| Create an empty dictionary that has a default value.
+-}
+empty : v -> DefaultDict k v
+empty v =
+    DefaultDict
+        { content = Dict.empty
+        , default = v
+        }
+
+{-| Get the value associated with the key. Uses the default if not found. -}
+get : comparable -> DefaultDict comparable v -> v
+get k (DefaultDict data) =
+    Dict.get k data.content |> Maybe.withDefault data.default
+
+{-| Insert a key-value pair into a dictionary with a default.
+-}
+insert : comparable -> v -> DefaultDict comparable v -> DefaultDict comparable v
+insert k v (DefaultDict data) =
+    DefaultDict { data | content = Dict.insert k v data.content }
+
+{-| "Remove" a value by making its value synchronize with the default value.
+-}
+remove : comparable -> DefaultDict comparable v -> DefaultDict comparable v
+remove k (DefaultDict data) =
+    DefaultDict { data | content = Dict.remove k data.content }
+
+{-| Update the default value of all unset keys.
+-}
+setDefault : v -> DefaultDict k v -> DefaultDict k v
+setDefault v (DefaultDict data) =
+    DefaultDict { data | default = v }
+
+{-| Update the value of a dictionary. The returned (or received) value is `Nothing`,
+it means the key synchronizes with the default value.
+-}
+update : comparable -> (Maybe v -> Maybe v) -> DefaultDict comparable v -> DefaultDict comparable v
+update k fv (DefaultDict data) =
+    DefaultDict { data | content = Dict.update k fv data.content }
+
+{-| Update the default value.
+-}
+updateDefault : (v -> v) -> DefaultDict k v -> DefaultDict k v
+updateDefault f (DefaultDict data) =
+    DefaultDict { data | default = f data.default }
diff --git a/src/Internal/Tools/Hashdict.elm b/src/Internal/Tools/Hashdict.elm
index 1835233..cd173ef 100644
--- a/src/Internal/Tools/Hashdict.elm
+++ b/src/Internal/Tools/Hashdict.elm
@@ -6,8 +6,10 @@ For example, this is used to store events by their event id, or store rooms by t
 
 -}
 
-import Dict exposing (Dict)
-
+import FastDict as Dict exposing (Dict)
+import Json.Decode as D
+import Json.Encode as E
+import Hash exposing (Hash)
 
 type Hashdict a
     = Hashdict
@@ -20,6 +22,12 @@ empty : (a -> String) -> Hashdict a
 empty hash =
     Hashdict { hash = hash, values = Dict.empty }
 
+encode : Hashdict E.Value -> E.Value
+encode (Hashdict h) =
+    h.values
+        |> Dict.toList
+        |> E.object
+
 
 fromList : (a -> String) -> List a -> Hashdict a
 fromList hash xs =
@@ -46,6 +54,9 @@ keys : Hashdict a -> List String
 keys (Hashdict h) =
     Dict.keys h.values
 
+toList : Hashdict a -> List (String, a)
+toList (Hashdict h) =
+    Dict.toList h.values
 
 union : Hashdict a -> Hashdict a -> Hashdict a
 union (Hashdict h1) (Hashdict h2) =
diff --git a/src/Internal/Tools/Iddict.elm b/src/Internal/Tools/Iddict.elm
new file mode 100644
index 0000000..c5fbafa
--- /dev/null
+++ b/src/Internal/Tools/Iddict.elm
@@ -0,0 +1,40 @@
+module Internal.Tools.Iddict exposing (..)
+{-| The id-dict stores values and gives them a unique id.
+-}
+
+import FastDict as Dict exposing (Dict)
+
+type Iddict a
+    = Iddict 
+        { cursor : Int
+        , dict : Dict Int a
+        }
+
+empty : Iddict a
+empty =
+    Iddict
+        { cursor = 0
+        , dict = Dict.empty
+        }
+
+get : Int -> Iddict a -> Maybe a
+get k (Iddict { dict }) =
+    Dict.get k dict
+
+insert : a -> Iddict a -> (Int, Iddict a)
+insert v (Iddict d) =
+    ( d.cursor
+    , Iddict { cursor = d.cursor + 1, dict = Dict.insert d.cursor v d.dict }
+    )
+
+keys : Iddict a -> List Int
+keys (Iddict { dict }) =
+    Dict.keys dict
+
+remove : Int -> Iddict a -> Iddict a
+remove k (Iddict d) =
+    Iddict { d | dict = Dict.remove k d.dict }
+
+values : Iddict a -> List a
+values (Iddict { dict }) =
+    Dict.values dict
\ No newline at end of file
diff --git a/src/Internal/Values/Timeline.elm b/src/Internal/Values/Timeline.elm
index 628527a..2c362e5 100644
--- a/src/Internal/Values/Timeline.elm
+++ b/src/Internal/Values/Timeline.elm
@@ -1,23 +1,113 @@
 module Internal.Values.Timeline exposing (..)
-
-{-| This module shapes the Timeline type used to keep track of timelines in Matrix rooms.
+{-| The Timeline can be very complex, and it can be represented in surprisingly
+complex manners. This module aims to provide one single Timeline type that
+accepts the complex pieces of information from the API and contain it all in
+a simple way to view events.
 -}
 
+import FastDict as Dict exposing (Dict)
 import Internal.Config.Leaking as Leaking
 import Internal.Tools.Fold as Fold
 import Internal.Values.Event as Event exposing (IEvent)
 import Internal.Values.StateManager as StateManager exposing (StateManager)
+import Internal.Tools.DefaultDict as DefaultDict exposing (DefaultDict)
+import Internal.Tools.Hashdict as Hashdict exposing (Hashdict)
+import Internal.Tools.Iddict as Iddict exposing (Iddict)
+import Internal.Tools.Filters.Main as Filter exposing (Filter)
+import Internal.Config.Leaking exposing (nextBatch)
 
+{-| The Timeline is a comprehensive object describing a timeline in a room.
 
+Any Timeline type contains the following pieces of information:
+
+- `events` Comprehensive dictionary containing all locally stored timeline events
+- `batches` Comprehensive dictionary containing all batches. Batches are pieces 
+    of the timeline that have been sent by the homeserver.
+- `token` Dictionary that maps for each batch token which batches it borders
+- `mostRecentSync` Id of the most "recent" batch in the timeline
+-}
 type Timeline
     = Timeline
-        { prevBatch : String
-        , nextBatch : String
-        , events : List IEvent
-        , stateAtStart : StateManager
-        , previous : BeforeTimeline
+        { events : Hashdict IEvent
+        , batches : Iddict TimelineBatch
+        , token : DefaultDict String (List Int)
+        , mostRecentSync : Maybe Int
         }
 
+{-| A BatchToken is a token that has been handed out by the server to mark the end of a  -}
+type alias BatchToken = String
+
+type alias TimelineBatch =
+    { prevBatch : List Batch
+    , nextBatch : List Batch
+    , filter : Filter
+    , events : List String
+    , stateDelta : StateManager
+    }
+
+type Batch
+    = Token BatchToken
+    | Batch Int
+
+addNewSync :
+    { events : List IEvent
+    , filter : Filter
+    , limited : Bool
+    , nextBatch : String
+    , prevBatch : String
+    , stateDelta : Maybe StateManager
+    } -> Timeline -> Timeline
+addNewSync data (Timeline timeline) =
+    let
+        batchToInsert : TimelineBatch
+        batchToInsert =
+            { prevBatch = 
+                [ Just <| Token data.prevBatch
+                , Maybe.map Batch timeline.mostRecentSync
+                ]
+                    |> List.filterMap identity
+            , nextBatch =
+                [ Token data.nextBatch ]
+            , filter = data.filter
+            , events = List.map Event.eventId data.events
+            , stateDelta = Maybe.withDefault StateManager.empty data.stateDelta
+            }
+    in
+        case Iddict.insert batchToInsert timeline.batches of
+            ( batchId, batches ) ->
+                Timeline
+                    { events = List.foldl Hashdict.insert timeline.events data.events
+                    , batches = batches
+                    , mostRecentSync = Just batchId
+                    , token =
+                        timeline.token
+                            |> DefaultDict.update data.prevBatch
+                                (\value ->
+                                    case value of
+                                        Just v ->
+                                            Just (batchId :: v)
+                                        Nothing ->
+                                            Just [ batchId ]
+                                )
+                            |> DefaultDict.update data.nextBatch
+                                (\value ->
+                                    case value of
+                                        Just v ->
+                                            Just (batchId :: v)
+                                        Nothing ->
+                                            Just [ batchId ]
+                                )
+                    }
+
+-- type Timeline
+--     = Timeline
+--         { prevBatch : String
+--         , nextBatch : String
+--         , events : List IEvent
+--         , stateAtStart : StateManager
+--         , previous : BeforeTimeline
+--         }
+
 
 type BeforeTimeline
     = Endless String
diff --git a/src/Matrix/RoomInvite.elm b/src/Matrix/RoomInvite.elm
index 1a9706c..7b4665b 100644
--- a/src/Matrix/RoomInvite.elm
+++ b/src/Matrix/RoomInvite.elm
@@ -32,10 +32,8 @@ Once you have the event you want, you can explore it with the following function
 
 import Internal.Api.VaultUpdate exposing (VaultUpdate)
 import Internal.Invite as Internal
-import Internal.Tools.Exceptions as X
 import Internal.Values.RoomInvite as IR
 import Json.Encode as E
-import Task exposing (Task)
 
 
 {-| The `RoomInvite` type serves as an invite to a given room.