The spermatids (a cell produced by meiotic division of a secondary spermatocyte and containing a nucleus, golgi apparatus, centriole and mitochondria) are slowly transformed into spermatozoa (sperms) by the process called spermiogenesis.
Spermiogenesis is the final stage of spermatogenesis.
The process of spermiogenesis can be divided into four stages: golgi phase, cap phase, formation of tail, and maturation stage
After spermiogenesis, sperm heads become embedded in the Sertoli cells, and are finally released from the seminiferous tubules by the process called spermiation (release of mature spermatozoa from the Sertoli cells).
FSH causes the Sertoli cells to secrete some factors (androgen-binding protein (ABP)) which stimulate the process of spermiogenesis.