Foetal skin. Coloured scanning electron micrograph (SEM) of the surface of the skin of a foetus. The skin is covered in microscopic folds (pink). The outer layer of the skin, the epidermis, is formed by the end of the fourth month of pregnancy. The epidermis is composed of four layers at this stage, the outer of which is known as the horny layer. The horny layer has a tough, scale-like surface formed from closely-packed dead cells. These cells are usually shed during the latter part of pregnancy. Magnification: x1000 at 6x7cm size.