Salamanders are the superstars of regeneration. They can grow back not only limbs but also tails, parts of their hearts and the retinas and lenses in their eyes. Humans cannot do any of that. So scientists hope that the salamander’s tricks may one day be applied to people. Natural regeneration, which might be accomplished with drugs or genes, would be easier than transplanting, researchers say. And the tissue would be the patient’s own, doing away with the problem of rejection.