Scientists have grown an entire rat arm in the laboratory for the first time.The incredible lab-grown rat forearm limb has blood vessels, muscle tissue, skin and it even moves. This involves taking organs from donors and stripping all the soft tissue away, leaving just the collagen scaffold. They even attached the lab-grown arms to healthy rats and saw that the blood from the animal circulated around the new limb. The biolimb could eventually replace alternative bionic limbs in human.