CYTOMER is a relational database on organs/tissues, cell types, physiological systems and developmental stages, presently focussing on the human system. From this database, an ontology for anatomical, morphological structures for the human organism, including all embryonal stages, and the cell types constituting these structures is derived. Shown below (left) is the searchable taxonomy of organs and other anatomical entities which forms the backbone of the ontology. On the right, detailed additional information for the particular entity is given.