The formation of male sex cells or sperm is called _spermatogenesis_. It is a complex process that takes place in the seminiferous tubules of the testes. Spermatogenesis begins with the production of spermatogonia, which are diploid cells that undergo mitosis to produce primary spermatocytes. The primary spermatocytes then undergo meiosis to produce secondary spermatocytes, which in turn undergo meiosis to produce spermatids. The spermatids then mature into sperm. The process of spermatogenesis takes about 72 days.