Abstract
CYTOMER® is a relational database of organs/tissues, cell types, physiological systems and developmental stages that currently focuses on the human system. From this database, we have derived an ontology for anatomical and morphological structures for the human organism which includes all embryonic stages and the cell types constituting these structures. The ontology has been transferred to the OWL format and is freely available for download at http://cytomer.bioinf.med.uni-goettingen.de.