When I first saw this," says cell biologist Alejandro Sanchez Alvarado, "it was with total amazement."
This is a worm. It's called a planarian. It's about an inch long, and you'll find it gliding along the bottoms of rivers and ponds all over the world. It's very flat, like a moving bit of pasta — nothing special to look at, but it has a hidden talent that has made it famous. It can regrow its body parts better than almost any other animal on Earth.