Transmission electron micrograph (TEM) of the ultrastructure of the seminiferous epithelium showing two Sertoli cell nuclei adjacent to the basal lamina. At centre is a pachytene primary spermatocyte above which are three spermatids in the early phase of elongation. The spermatids have developed an acrosome which covers the basally-facing aspect of their nuclei. Magnification: x2,000 when height printed at 10cm.