The testicles are part of the male reproductive organ. They make sperm and the male sex hormone called testosterone. Without testicles, men wouldn't be able to have kids. They'd also look and feel a lot different without testosterone. Testosterone is responsible for many of the male characteristics that make men different from women. These important organs hang outside the body in a sac called the scrotum. And since they hang outside the body, they don't have bone or muscle around to protect them like other organs do. That means there is nothing to absorb any of the blow if they happen to get hit. So they take the full force of the hit without any cushion.