diff --git a/src/layer.ml b/src/layer.ml
index 85a9ce8..f98de08 100644
--- a/src/layer.ml
+++ b/src/layer.ml
@@ -118,7 +118,30 @@ let create_geojson : Jv.t -> geojson_opt list -> [ `Geojson ] t =
   let jv_t = Jv.call Global.leaflet "geoJSON" [| geojson; Jv.obj l |] in
   Geojson jv_t
 
+(** Tile layers *)
+
+let create_tile_osm : string option -> [ `Tile ] t =
+ fun url ->
+  let url =
+    Option.value url
+      ~default:"https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
+  in
+  let jv_t =
+    Jv.call Global.leaflet "tileLayer"
+      [| Jv.of_string url
+       ; Jv.obj
+           [| ( "attribution"
+              , Jv.of_string
+                  "&copy; <a \
+                   href=\"https://www.openstreetmap.org/copyright\">OpenStreetMap</a> \
+                   contributors" )
+           |]
+      |]
+  in
+  Tile jv_t
+
 (** Marker layers *)
+(* TODO make a Marker module? *)
 
 type marker_opt =
   | Icon of Icon.t
@@ -168,24 +191,28 @@ let create_marker : Latlng.t -> marker_opt list -> [ `Marker ] t =
   in
   Marker jv_t
 
-(** Tile layers *)
+let get_latlng : [ `Marker ] t -> Latlng.t = function
+  | Marker marker -> Jv.call marker "getLatLng" [||] |> Latlng.of_jv
 
-let create_tile_osm : string option -> [ `Tile ] t =
- fun url ->
-  let url =
-    Option.value url
-      ~default:"https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png"
-  in
-  let jv_t =
-    Jv.call Global.leaflet "tileLayer"
-      [| Jv.of_string url
-       ; Jv.obj
-           [| ( "attribution"
-              , Jv.of_string
-                  "&copy; <a \
-                   href=\"https://www.openstreetmap.org/copyright\">OpenStreetMap</a> \
-                   contributors" )
-           |]
-      |]
-  in
-  Tile jv_t
+let set_latlng latlng : [ `Marker ] t -> unit = function
+  | Marker marker ->
+    let (_ : Jv.t) = Jv.call marker "setLatLng" [| Latlng.to_jv latlng |] in
+    ()
+
+let set_z_index_offset z_index : [ `Marker ] t -> unit = function
+  | Marker marker ->
+    let (_ : Jv.t) = Jv.call marker "setZIndexOffset" [| Jv.of_int z_index |] in
+    ()
+
+let get_icon : [ `Marker ] t -> Icon.t = function
+  | Marker marker -> Jv.call marker "getIcon" [||] |> Icon.of_jv
+
+let set_icon icon : [ `Marker ] t -> unit = function
+  | Marker marker ->
+    let (_ : Jv.t) = Jv.call marker "setIcon" [| Icon.to_jv icon |] in
+    ()
+
+let set_opacity opacity : [ `Marker ] t -> unit = function
+  | Marker marker ->
+    let (_ : Jv.t) = Jv.call marker "setOpacity" [| Jv.of_int opacity |] in
+    ()
diff --git a/src/layer.mli b/src/layer.mli
index e819d2e..84586d7 100644
--- a/src/layer.mli
+++ b/src/layer.mli
@@ -62,6 +62,13 @@ type geojson_opt =
 (** [create_geojson geojson] is a new geojson layer *)
 val create_geojson : Jv.t -> geojson_opt list -> [ `Geojson ] t
 
+(** Tile layers *)
+
+(** [create_tile_osm Some(url)] is a new tile layer with tile server specified
+    by [url]. Tile server default to [openstreetmap.org]. See
+    {:https://wiki.openstreetmap.org/wiki/Tile_servers} *)
+val create_tile_osm : string option -> [ `Tile ] t
+
 (** Marker layers *)
 
 (** type for marker option, used to create marker *)
@@ -83,9 +90,20 @@ type marker_opt =
     [latlng] and with options set to [options] *)
 val create_marker : Latlng.t -> marker_opt list -> [ `Marker ] t
 
-(** Tile layers *)
+(** Returns the current geographical position of the marker. *)
+val get_latlng : [ `Marker ] t -> Latlng.t
 
-(** [create_tile_osm Some(url)] is a new tile layer with tile server specified
-    by [url]. Tile server default to [openstreetmap.org]. See
-    {:https://wiki.openstreetmap.org/wiki/Tile_servers} *)
-val create_tile_osm : string option -> [ `Tile ] t
+(** Changes the marker position to the given point. *)
+val set_latlng : Latlng.t -> [ `Marker ] t -> unit
+
+(** Changes the zIndex offset of the marker. *)
+val set_z_index_offset : int -> [ `Marker ] t -> unit
+
+(** Returns the current icon used by the marker *)
+val get_icon : [ `Marker ] t -> Icon.t
+
+(** Changes the marker icon. *)
+val set_icon : Icon.t -> [ `Marker ] t -> unit
+
+(** Changes the opacity of the marker. *)
+val set_opacity : int -> [ `Marker ] t -> unit