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