The term "regeneration" in biology can refer to the regrowth of a severed limb in some animals, but it's not a simple process; the complexity varies wildly, even between closely related species. Some salamanders regrow limbs perfectly, while others can only manage a less-functional stump. elaborate
Cryobiology involves techniques to cool biological materials down to extremely low temperatures, sometimes even below -196°C (the boiling point of liquid nitrogen), preserving them for later use. elaborate
Bird feathers, initially evolved for insulation (their original function), were later exapted for flight. elaborate