Advances in medical technology have helped us live longer. Now, researchers are exploring ways to repair, refurbish, or replace human organs that have been damaged by chronic disease, traumatic injury, heart attack, stroke, or just plain aging.

"Medicine is saving people who previously we weren't able to save," says Dr. Doris A. Taylor, director of regenerative medicine research at the Texas Heart Institute in Houston.

Even so, demand for donor organs exceeds the number available. "Each year thousands of people die while waiting for an organ," Taylor says. That gap in supply and demand is one factor that has led researchers to ever more innovative treatments; at times these treatments can sound like science fiction come to life.

Here's a look