If a tadpole loses its tail, it can simply grow another. The process takes less than a week. Humans can only dream of such amazing regeneration and many scientists are trying to understand how it works. Now, Nick Love from the University of Manchester has found that the tadpole’s healing powers depend on a group of chemicals that are often caricaturised as unwanted villains.

They’re called “reactive oxygen species” (ROS), or more colloquially as “free radicals”—small molecules that contain oxygen atoms and are highly reactive. We produce them through the act of living, and we depend on them to coordinate the various chemical events within our cells. But when their numbers increase, ROS can wreak havoc on our cells