Among animals, the sponges, coelenterates, and the simpler worms show remarkable power of regeneration. They can be cut in pieces and each piece can grow into a new animal. Starfishes can grow new arms. Crayfishes can grow new claws, eyes, and legs. Lizards can grow new tail.
Salamanders can regenerate lost limbs.
People and other mammals can regenerate only hair, nails, skin, and a few other tissues. In some cases, a different sort of tissue grows over the damaged area and forms a scar. Human fingers do not grow back.