Spermiogenesis is the last phase in the formation of spermatozoa. During this stage of maturation, the spermatid cells see an increase in the size of the tail and a decrease in the spermatozoa head. This series of complex transformations result in the final constitution of the spermatozoa, the male cells that transfer DNA to the oocyte. The mature sperm is released through the seminiferous tubules, which are small tubes inside the testicles, responsible for producing sperm and the hormone testosterone. The approximate duration of this process is two and a half months.