Tissue engineering is a relatively new field of basic and clinical science that is concerned, in part, with creating tissues that can augment or replace injured, defective, or diseased body parts. The approach to fabricating the tissues involves adding specific cell types to grow on a polymer scaffold having the shape of the tissue to be restored. The scaffold gradually disappears, while the cells continue developing in the scaffold shape. With the use of non-human animal cells, there has been considerable recent progress made in the engineering of skin, bladder, cartilage, and several other tissues.