Illustration of precursor sperm cells known as spermatocytes (three larger cells) and spermatids (four smaller cells) within a seminiferous tubule in a testis (testicle). The spermatocytes divide via two stages of meiosis to form haploid (containing one set of chromosomes) spermatids, which will in turn mature into spermatozoa, or sperm. Spermatozoa are the mobile male gametes (reproductive cells), which can fertilise the egg during sexual reproduction, and carry one set of chromosomes from one parent.