What do starfish, salamanders, and the Hulk have in common? They all have the power of regeneration. Starfish can regenerate their legs; salamanders can do that and a few better by regrowing their tail, and parts of their heart and eyes. The Hulk, well, the Hulk can regenerate it all. We ordinary humans are not so lucky. If we lose something, it's gone for good, unless, that is, we happen to have a brother working in the field of regenerative medicine.