Scientists have discovered the ultimate case of regeneration: some decapitated sea slugs can regrow hearts and whole new bodies. This “wonder of nature,” reported in a biology journal on Monday, could eventually help scientists better understand and tackle regeneration of human tissue. Biology researcher Sayaka Mitoh said she loves studying Japanese sea slugs because they are small, cute and weird. They can even briefly photosynthesize like a plant drawing food from the sun. One day in the lab, she saw something bizarre: a sea slug had decapitated itself and the head kept on moving and living. Then a couple more did the same, according to a study in Current Biology.