The multiplication and development of germ cells in the seminiferous tubules of the testiclesoccur through a complex series of cellular events that are controlled by multiple signals. It is composed of 6 stages in humans (Figure 1).

Spermatogonial stem cells are self-renewed via mitosis, meiosis and contribute to the formation of haploid spermatids from diploid spermatocytes. Through the process of spermiogenesis, spermatids undergo maturation and are transformed into functional spermatozoa which are released at spermiation after the breakage of intercellular bridges attaching the spermatids to Sertoli cells. Spermatogenesis is a continuous process requiring the contribution of numerous cell and regulatory factors. Its understanding is essential in order to advance research for treatment of male infertility. The different stages of spermatogenesis along with the main roles of Sertoli cell and BTB will be reviewed. Some emerging fields in research regarding the new classification was briefly examined for a better understanding of the complexity of the process.