This animal can regrow a limb, a tail, or even part of its brain

The axolotl is a Mexican amphibian that — unlike most animals — keeps its larval form for its entire life (a phenomenon called neoteny) and never fully undergoes metamorphosis.

When an axolotl loses a leg, its tail, or even part of its spinal cord, a cluster of stem cells called a blastema forms at the wound site, and within a few weeks it regrows a fully functional, complete limb — bones, muscles, nerves, and blood vessels included.

The regeneration happens almost without scarring, which sets the axolotl apart from most mammals, where damaged tissue typically heals by scarring over rather than fully rebuilding the original structure.

That makes the axolotl one of the most intensively studied animals in regenerative medicine — scientists are trying to figure out why human cells can't do the same thing.