Now, testosterone has many important functions. Firstly, it basically stimulates and initiates the production of our sperm cells inside these regions between our surtoli cells. And we'll discuss what the function of sirtoli cells are in just a moment. Now, it also causes, it initiates secondary sex characteristics including the growth of pubic hair as well as underarmpit hair. And it also enlarges our larynx and that is what gives us a deeper voice when we're undergoing puberty. Now, it also is responsible for initiating the process of puberty.