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Healing wound. Coloured scanning electron micrograph (SEM) of a healing wound on the skin, five days after injury. There is dried blood and a scab (red) over the wound. A scab consists of layers of keratinocytes (skin cells that contain the protein keratin) and forms a hard protective layer over the wound. Beneath the scab the skin is healing; the damaged tissue is being replaced with collagen fibres. However, the new tissue is not rebuilt in exactly the same way as the old. This results in a scar, a thicker paler area that does not carry out the same functions as the lost skin. At centre left is the end of a stitch. Magnification: x125 when printed at 10 centimetres wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/CHR 366 EYE OF SCIENCE/SCIENCE PHOTO LIBRARY) === ===