The term spermatid refers to the haploid male germ cell that results from secondary spermatocyte division. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte.
When formed, early round spermatids must undergo further maturational events in order to develop into spermatozoa, a process termed spermiogenesis (also termed spermeteliosis). The spermatids begin to grow a tail, develop a thickened mid-piece where the mitochondria become localised and form an acrosome. Spermatid DNA also undergoes packaging, becoming highly condensed. The DNA is packaged firstly with specific nuclear basic proteins, which are subsequently replaced with protamines during spermatid elongation. The resultant tightly packed chromatin is transcriptionally inactive.