Sperm production. Coloured scanning electron micrograph (SEM) of sperm cells (spermatozoa) in the seminiferous tubules of the testis. This is the site of spermatogenesis (sperm production). Each sperm cell consists of a head (yellow), which contains the genetic material that fertilises the female egg cell, and a tail (blue), which propels the sperm. The heads of the sperm are buried in Sertoli cells (orange), which nourish the developing sperm.