Transmission electron micrograph (TEM) of the ultrastructure of the seminiferous epithelium of the human testis. Near the basal lamina is a Sertoli cell with many lipid inclusions (grey circles) and a spermatogonium and a primary spermatocyte. Another Sertoli cell nucleus is seen within a column of its own cytoplasm. At this higher level are numerous large rounded primary spermatocytes which are supported by ramifications of Sertoli cell cytoplasm. More apically are elongating spermatids with acrosomal caps covering the cranial aspect of their nuclei. Magnification: x1,000 when height printed at 10cm.