Scientific American Frontiers on PBS

This episode explores what host Alan Alda calls “the new marriage of biology and engineering” in repairing and replacing damaged body parts. Among the advances: mechanical hearts; functional electrical stimulation for people with spinal-cord injuries; and a bioreactor that functions like a liver (“It's not just chipped liver,” quips MIT scientist Linda Griffith). Then there's stem-cell research (some using cells from unfertilized eggs). It's promising, Alda says, because “if we just provide the right conditions, stem cells will do their thing.”