Skin expansion is a revolutionary technique for plastic surgery. Its principle is based on the observation of clinical facts, such as pregnancy, in which the skin can readily become distended. The technique consists in implanting a silicon prosthesis, connected to a filling valve through a tube, under the skin. The inflation of this prosthesis takes 3 months. At the end of this time, good-quality skin with the same features as normal skin (color, hairs, sensation) is available. There are many indications for this technique, including substance losses, removal of congenital tumors and of scars, breast reconstruction or scalp surgery.