Wired reports on efforts to replicate the ability of some animals to regenerate entire organs. "Lop off a newt's leg or tail, and it will grow a new one. The creature's cells can regenerate thanks to built-in time machines that revert cells to early versions of themselves in a process called dedifferentiation. Researchers who study this mechanism hope one day to learn how to induce the same 'cell time travel' in humans. If the cells go back far enough, they become stem cells, which researchers believe hold promise for treating many diseases. ... In newts and some other animals with the ability to regenerate, cells at the site of an injury can revert to their embryonic stem-cell stage and can become another type of cell in that creature's body."

Link: http://www.wired.com/news/print/0,1294,67155,00.html