Although penis extenders are a fairly new invention, the idea behind these devices has been known to humans for thousands of years. This principle says that human body is designed to adapt to external stimulus. For example, in order to build big and strong muscles, people usually lift weights. Naturally, the penis responds to traction the same way that any other part of the human anatomy does. The traction device slowly stretches and lengthens the penis, which makes its cells grow, ultimately making it larger. Penis extenders provide a combination of effectiveness and safety that no other method can match. Penis surgery works, but is very dangerous (not to mention expensive too.) In contrast, penis extenders went through extensive medical testing and are clinically proven to be safe and effective.