Planarians are small flatworms that live in wet and humid areas around the globe. Although these creatures are relatively simple, their small, soft bodies possess one of the most amazing secrets in the animal kingdom. Cut a planarian into as many as 279 pieces and, within a few weeks, each bit will regenerate into a full new worm – head, eyes, digestive system and all. This incredible ability raises interesting questions for philosophers, who might wonder which, if any, of these worms is the ‘original’, and for medical researchers, who are hoping to harness the adaptability of planarian’s powerful regenerative stem cells to help regrow tissue, and potentially even limbs, on humans. Read more about this video at KQED Science.