diff --git a/src/H5Fed_store.c b/src/H5Fed_store.c
index 8a4e126..dfbe747 100644
--- a/src/H5Fed_store.c
+++ b/src/H5Fed_store.c
@@ -18,22 +18,83 @@
 #include "h5/h5_types.h"
 #include "H5Fed.h"
 
-h5_int_t H5FedSetNumVertices (
-	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
-	const h5_size_t num_vertices	/*!< number of verices at level
-					  \c level			*/
+/*!
+  Add a new level.
+
+  \note
+  values for f->t.num_levels:
+  \c -1		unknown: after opening the file. This is equivalent to
+		"topological data has not been initialized".
+  \c 0		no levels: HDF5 group for meshes may already exist but must not!
+  \c > 0	number of mesh levels
+ 
+  \note
+  write new level:
+	H5FedAddLevel( f );
+	H5FedSetNumVertices( f, nv );
+	H5FedSetNumTetrahedra( f, nt );
+*/
+  
+h5_id_t H5FedAddLevel (
+	h5_file * f			/*!< file handle		*/
 	) {
-	return -1;
+	struct h5t_fdata *t = &f->t;
+
+	if ( f->mode == H5_O_RDONLY ) {
+		return -1;
+	}
+	if ( t->num_levels == -1 ) {	/* unknown number of levels	*/
+		/* determine number of levels */
+		return -1;		/* not implemented		*/
+	}
+	t->cur_level = t->num_levels++;
+
+	ssize_t num_bytes = t->num_levels*sizeof ( t->levels[0] );
+	t->levels = realloc ( t->levels, num_bytes );
+
+	struct h5t_fdata_level *level = t->levels[t->cur_level];
+
+	memset ( level, 0, sizeof ( *level ) );
+
+	level->new_level = 1;
+	level->last_stored_vertex = -1;
+	level->last_stored_tet = -1;
+
+	return t->cur_level;
 }
 
-h5_int_t H5FedSetNumTetrahedra (
+/*!
+  Set number of vertices in current step and level
+*/
+h5_int_t
+H5FedSetNumVertices (
+	h5_file * f,			/*!< file handle		*/
+	const h5_size_t num_vertices	/*!< number of verices at level	*/
+	) {
+	struct h5t_fdata_level *level = &f->t.levels[f->t.cur_level];
+	ssize_t num_bytes;
+
+	level->num_vertices = num_vertices;
+	num_bytes = num_vertices * sizeof( level->vertices[0] );
+	level->vertices = realloc ( level->vertices, num_bytes );
+
+	return num_vertices;
+}
+
+h5_int_t
+H5FedSetNumTetrahedra (
 	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
-	const h5_size_t num_tet		/*!< number of tetrahedra at
+	const h5_size_t num_tets	/*!< number of tetrahedra at
 					  level \c level		*/
 	) {
-	return -1;
+	struct h5t_fdata_level *level = &f->t.levels[f->t.cur_level];
+	ssize_t num_bytes;
+
+	level->num_tets = num_tets;
+	num_bytes = num_tets * sizeof( level->tets[0] );
+	level->tets = realloc ( level->tets, num_bytes );
+
+	return num_tets;
 }
 
 /*!
@@ -42,16 +103,30 @@ h5_int_t H5FedSetNumTetrahedra (
   Stores the the coordinates of a specific vertex at level \c level
   with id \c vertex_id of the tetrahedral mesh.
 
-  \return value \c >=0 on success
+  \return local vertex id on success
   \return \c -1 on error
 */
-h5_int_t H5FedStoreVertexCoordinate (
-	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
+h5_id_t
+H5FedStoreVertex (
+	h5_file * f,			/*!< file handle		*/
 	const h5_id_t vertex_id,	/*!< global vertex id		*/
-	const h5_vertex * const vertex	/*!< 3-tuple of coordinates	*/
+	const h5_float64_t P[3]		/*!< coordinates		*/
 	) {
-	return -1;
+
+	struct h5t_fdata *t = &f->t
+
+	if ( t->cur_level < 0 ) return -1;
+
+	struct h5t_fdata_level *level = t->levels[t->cur_level];
+	if ( level->last_stored_vertex+1 >= level->num_vertices ) 
+		return -1;
+
+	h5_vertex *vertex = level->vertices[++level->last_stored_vertex];
+	vertex->id = vertex_id;
+	vertex->level = t->cur_level;
+	memcpy ( vertex->P, P, sizeof ( P ) );
+	
+	return level->last_stored_vertex;
 }
 
 /*!
@@ -60,16 +135,16 @@ h5_int_t H5FedStoreVertexCoordinate (
   Stores the 2-tuple, that contains the specific indices describing
   an edge with id \c edge_id at level \c level of the tetrahedral mesh.
 
-  \return value \c >=0 on success
+  \return local edge id
   \return \c -1 on error
 */
-h5_int_t H5FedStoreEdge (
+h5_id_t
+H5FedStoreEdge (
 	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
 	const h5_id_t edge_id,		/*!< global edge id		*/
 	const h5_id_t parent_id,	/*!< parent id if level \c >0
 					  else \x -1			*/
-	const h5_edge * const edge	/*!< 2-tuple with vertex id's	*/
+	const h5_id_t edge[2]		/*!< tuple with vertex id's	*/
 	) {
 	return -1;
 }
@@ -80,16 +155,16 @@ h5_int_t H5FedStoreEdge (
   Stores the 3-tuple, that contains the specific indices describing a
   triangle with id \c triangle_id at level \c level of the tetrahedral mesh.
 
-  \return value \c >=0 on success
+  \return local triangle id
   \return \c -1 on error
 */
-h5_int_t H5FedStoreTriangle (
+h5_int_t
+H5FedStoreTriangle (
 	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
 	const h5_id_t triangle_id,	/*!< global triangle id		*/
 	const h5_id_t parent_id,	/*!< parent id if level \c >0
 					     else \x -1			*/
-	const h5_triangle * const triangle/*!< 3-tuple with vertex id's	*/
+	const h5_id triangle[3]		/*!< tuple with vertex id's	*/
 	) {
 	return -1;
 }
@@ -101,18 +176,33 @@ h5_int_t H5FedStoreTriangle (
   a tetrahedron with id \c tet_id at level \c level of the tetrahedral
   mesh.
 
-  \return value \c >=0 on success
+  \return local tetrahedron id
   \return \c -1 on error
 */
-h5_int_t H5FedStoreTetrahedron (
+h5_int_t
+H5FedStoreTetrahedron (
 	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
 	const h5_id_t tet_id,		/*!< global tetrahedron id	*/
 	const h5_id_t parent_id,	/*!< parent id if level \c >0
-					  else \x -1			*/
-	const h5_tetrahedron * const tet/*!< 4-tuple with vertex id's	*/
+					     else \x -1			*/
+	const h5_id_t tet[4];		/*!< tuple with vertex id's	*/
 	) {
-	return -1;
+
+	struct h5t_fdata *t = &f->t
+
+	if ( t->cur_level < 0 ) return -1;
+
+	struct h5t_fdata_level *level = t->levels[t->cur_level];
+	if ( level->last_stored_tet+1 >= level->num_tets ) 
+		return -1;
+
+	h5_tetrahedron *tet = level->tets[++level->last_stored_tet];
+	tet->id = tet_id;
+	tet->level = t->cur_level;
+	memcpy ( tet->vertex_ids, tet, sizeof ( tet ) );
+	
+	return level->last_stored_vertex;
+
 }
 
 /*!
@@ -122,16 +212,15 @@ h5_int_t H5FedStoreTetrahedron (
   a boundary triangle \c btriangle with id \c btriangle_id at level
   \c level of the tetrahedral mesh.
 
-  \return value \c >=0 on success
+  \return local boundary triangle id
   \return \c -1 on error
 */
 h5_int_t H5FedStoreBoundaryTriangle (
 	h5_file * fh,			/*!< file handle		*/
-	const h5_id_t level,		/*!< mesh level			*/
 	const h5_id_t btriangle_id,	/*!< global boundary triangle id*/
 	const h5_id_t parent_id,	/*!< parent id if level \c >0
 					     else \c -1			*/
-	const h5_triangle * const btriangle/*!< 3-tuple with vertex id's*/
+	const h5_id_t btriangle[3]	/*!< tuple with vertex id's*/
 	) {
 	return -1;
 }