In mammals, Spermatogonial stem cells (SSCs) are unique because they are the only adult stem cells that can contribute to the next generation. SSCs are adult stem cells located on the basement membrane of the seminiferous tubules. SSCs have the capacity to self renew and produce daughter cells that commit to differentiate into spermatozoa throughout adult reproductive life of male through spermatogenesis. In mammals, SSCs constitute a very small fraction of the adult testicular germ cells. Approximately 30,000 SSCs exist in each adult mouse testis and are located in the most peripheral region of the seminiferous tubule. Spermatogonial stem cells constitute only 0.03% of the total germ cell population in rodent and human testis.