Transmission electron micrograph (TEM) of the ultrastructure of an elongating human spermatid located within a column of Sertoli cell cytoplasm in the seminiferous epithelium. The cell DNA (deoxyribonucleic acid) has compacted into a pyriform-shaped nucleus to which is attached part of the developing sperm tail or flagellum. Covering the leading surface of the nucleus is the acrosome. The spermatid cytoplasm is being extruded distally and will ultimately be discarded when the sperm is released from the Sertoli cell in the process termed spermiation. Magnification: x8,000 when height printed at 10cm.