Pig testicle, light micrographs. The bottom micrograph shows a seminiferous tubule surrounded by Leydig cells (light blue). In the right micrograph, the cell types of the male germinal epithelium have been marked with colour. Seen are; Sertoli cells (yellow), spermatids (green) and primary spermatocytes, with zygotene phase cells in pink and pachytene phase cells in blue.