Axolotls can regrow lost limbs, and even parts of their heart and brain.
If an axolotl loses a leg, it grows a complete new one with bones, muscles and nerves, without scarring. The same works for the tail, the spinal cord and pieces of the heart and brain.
Why is this true?
Cells at the wound site revert to a stem-cell-like state and rebuild the missing structure from a blueprint that most animals switch off after embryonic development. That is why axolotls are studied so intensely in medicine.
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More about animals
Animals are the easiest place to find facts that sound invented. Three hearts, blue blood, cube-shaped droppings, a punch fast enough to boil water for an instant — every one of these is ordinary biology to the animal doing it. The collection here leans on well-documented behaviour and anatomy rather than folklore, so each entry comes with a short explanation of why the trick actually works and a source you can read next.