Testicles produce sperm and the hormone testosterone.
Sperm grows at the back of the testicle, in the epididymis. The testicles hang in a sack, called the scrotum, that sits outside of the body because it is necessary for sperm to be stored at a temperature that is slightly below that of the body. In doing so, a man becomes familiar with his body and will notice any changes. Testicular cancer, although rare, can be fatal if not detected early enough. A TSE can best be done in the shower because the hot water relaxes the scrotum and soap reduces friction while examining.