Human testicle, light micrographs. The bottom micrograph shows a seminiferous tubule. In the top micrograph the cell types of the male germinal epithelium have been marked with colour. Seen are; Sertoli cells (light blue), elongated spermatids (red) and primary spermatocytes in meiosis, with zygotene phase cells in blue and pachytene phase cells in green.