The scrotum is the sack of skin that hangs behind the penis. Inside, are the testicles, which are two small structures more commonly called �balls.�  Inside the testes, sperm cells are made and stored.  These are the cells that come out of the penis during ejaculation, or when a guy cums. They can swim through a female�s body searching for an egg to fertilize. If they connect with one, they can start a pregnancy.

The sex hormone, testosterone, is also produced in the testicles. Like the female hormone, estrogen, the male hormone gives men their special traits � muscles, deeper voices, more hair on the body and stuff like that.

Sperm need a specific temperature to survive. The scrotum makes sure the temperature is right for sperm to survive. So, when it�s real warm, the scrotum stretches and the testicles hang lower and away from the warmth of the body. When it�s cold outside, the scrotum pulls the testicles close to the body to keep them warm. When guys wear tight-fitting pants or underwear or sit too much, the scrotum can�t do its job and sperm are less likely to survive or be able to swim.