"Don't cross your eyes -- they'll stick that way!" That's something most of us have heard from our mothers at one time or another. Can your eyes really get stuck?
WHAT'S INSIDE: HUMAN BODY
- Body Parts
- Body Systems
You breathe in and out anywhere from 15 to 25 times per minute without even thinking about it -- it just happens naturally. Learn all about your lungs, various conditions and diseases, and what makes the breath of life so crucial.
Why don't you have two hearts? Here's a hint: It's the same reason why you have one liver, but two eyes. Would a second heart help you live better?