Testes
Testes
The testes are part of the male reproductive organs and are where the sperm is produced.
Spermatogenesis takes place at a lower temperature than regular body temperature which is why the testes are outside the body surrounded by a pouch of skin which is called the scrotum. This regulates the tempterature and keeps it at the optimum.
References
Sadava et al. (2012). LIFE The Science Of Biology. 10th ed. Sunderland: Sinauer Associates. 889.