Spermatogenesis is a complex process involving stages of spermatocytogenesis, spermatidogenesis and spermiogenesis. It is defined as the process of producing haploid sperm cells from primordial diploid germ cells in the seminiferous tubules of the testis. Hormonal role at each stage of spermatogenesis and signaling or regulatory pathways that is associated with the process has been discussed in this chapter. The factors that alters spermatogenesis which spans through hormones, medication, temperature, toxins etc., are further explained. Diagrams showing the stages of spermatogenesis and tables, which explains various alterations in genetic materials resulting in disorders of spermatogenesis, are also explained. The various stages and phases in each processes of spermatogenesis have been explained in detail. Also, chromosomal changes and cellular divisions that constitute spermatogenesis are further discussed. Finally, the role of calcium in spermatogenesis is discussed.