When men of the Walibri tribe of central Australia greet each other, they shake penises instead of hands.

Evey year on March 15 Japan throws a giant festival to celebrate the penis and fertility.

A 900-pound wooden phallus is paraded around the streets of the town Komaki, and women carry massive dildos in their arms.

Thousands of people come to pay homage to the penis and take part in the festivities.

Use it or loose it! Lack of sexual activity has been shown to cause penis size to decrease.

Best ways to improve sexual function: stop smoking, start exercising, loose weight.

The word "penis" comes from the Latin word for "tail".

All penises bend slightly to the left or right -- there is no perfectly straight penis.