ommatidium

http://purl.obolibrary.org/obo/UBERON_0000971

The smallest morphological and functional unit of the compound eye that consists of a usually limited and often constant number of rhabdomeric photoreceptor cells, cornea-secreting epithelial cells, and interommatidial pigment cells, and may additionally contain crystalline cone cells. [ http://www.ncbi.nlm.nih.gov/pubmed/21062451 ]

Synonyms: omatidium