The axolotl, which is a type of salamander, is the only known amphibian that can fully regenerate its limbs, spinal cord, heart, and other organs. It has the ability to repair or replace damaged or missing tissues with brand new ones. This makes the axolotl a valuable animal model for medical research, as it may hold the key to developing new regenerative therapies for humans. However, the axolotl is currently critically endangered in the wild, due to pollution, habitat loss, and capture for the pet trade.