If a starfish loses an arm, it's no big deal. A starfish has regenerative capabilities, so the starfish can grow a new arm. In fact, you can cut a starfish in half and each piece could regenerate, forming two separate starfish! Lots of other organisms have ways to regenerate. Some lizards and salamanders can grow new tails and some insects can grow new legs.

Wouldn't it be great if we could repair ourselves in the same way? Imagine losing an arm in an accident, and then growing a new one two weeks later!

Okay, that's impossible. But your body can do a little regeneration of its own. For example, if you wipeout on your skateboard or cut yourself while making dinner, your epidermis (skin) can regenerate to heal the wound. If you were to cut off your fingertip in woodworking class, you might even grow another one (as long as the cut is above your fingernail bed, the area where your fingernail starts to grow). The new tip probably wouldn't look exactly like what you lost, though.

Will you ever be able to grow a new arm? Maybe! Scientists are working with a type of cell called a stem-cell. These special cells might let humans regenerate. Maybe in the future we can grow new body parts.

But what can we do right now to help people who need new body parts? From head to toe, there are already lots of "bionic body parts" that doctors can use. Let's take a closer look at a few of them.