A tiny worm that regenerates entire organs. A South American snail that can regrow its eyes. A killifish that suspends animation in dry weather and reanimates in water. These are the organisms at the heart of regeneration science. But exactly how they do these things is still a mystery to scientists. Today on the show, Regina G. Barber talks to microbiologist Alejandro Sánchez Alvarado about this mystery. They get into what regeneration looks like, why humans can't do it (yet) and where the science may lead us in the decades to come. Listen to Short Wave on Spotify, Apple Podcasts and Google Podcasts.Have a science mystery? Send us your questions to shortwave@npr.org.