EurekAlert reports on the state of tissue engineering, from knees to hearts and even brains. Tissue engineering is a branch of regenerative medicine in which scientists are attempting to build structures from scaffolds and tissue to replace damaged portions of the body. Researchers are now regularly growing undifferentiated tissue like skin and cartilage; the trick is to create structure, as in heart valves, bone, joints and other organs. Eventually, tissue engineers hope to produce entire organs for transplant, grown from a patient's own cells. All in all, this is the infancy of a very challenging field, but the rewards will be enormous. Tens of thousands of lives could be saved each and every day if new organs could be grown on demand.