Your Ribs
Your heart, lungs, and liver are all very important, and luckily you've got ribs to keep them safe. Ribs act like a cage of bones around your chest. It's easy to feel this cage by running your fingers along the sides and front of your body, a few inches below your heart. If you breathe in deeply, you can easily feel your ribs right in the front of your body, too. Some thin kids can even see a few of their ribs right through their skin.

Your ribs come in pairs, and the left and right sides of each pair are exactly the same. Most people have 12 pairs of ribs, but some people are born with one or more extra ribs, and some people might have one pair less.

All 12 pairs of ribs attach in the back to the spine, where they are held in place by the thoracic vertebrae. The first seven pairs of ribs attach in the front to the sternum (say: stur-num), a strong bone in the center of your chest that holds those ribs in place. The remaining sets of ribs don't attach to the sternum directly. The next two or three pairs are held on with cartilage to the ribs above them.

The very last two sets of ribs are called floating ribs because they aren't connected to the sternum or the ribs above them. But don't worry, these ribs can't ever float away. Like the rest of the ribs, they are securely attached to the spine in the back.

Your Skull
Your skull protects the most important part of all, the brain. You can feel your skull by pushing on your head, especially in the back a few inches above your neck. The skull is actually made up of different bones. Some of these bones protect your brain, whereas others make up the structure of your face. If you touch beneath your eyes, you can feel the ridge of the bone that forms the hole where your eye sits.

And although you can't see it, the smallest bone in your whole body is in your head, too. The stirrup bone behind your eardrum is only .1 to .13 inches (2.6 to 3.3 millimeters) long! Want to know something else? Your lower jawbone is the only bone in your head you can move. It opens and closes to let you talk and chew food.

Your skull is pretty cool, but it's changed since you were a baby. All babies are born with spaces between the bones in their skulls. This allows the bones to move, close up, and even overlap as the baby goes through the birth canal. As the baby grows, the space between the bones slowly closes up and disappears, and special joints called sutures (say: soo-churs) connect the bones.