The Vacanti mouse was a laboratory mouse (circa 1996) that had what looked like a human ear grown on its back. The "ear" was actually an ear-shaped cartilage structure grown by seeding cow knee cartilage cells into biodegradable ear-shaped mold and then implanted under the skin of the mouse, with an external ear-shaped splint to maintain the desired shape. Then the cartilage naturally grew by itself within the restricted shape and size. The splint was removed briefly to take the publicity pictures, which is very controversial.