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Human skin (epidermis), coloured scanning electron micrograph (SEM). Outer surface layer, the stratum corneum (cornified layer). It is formed from flattened, dead skin cells. The scaly appearance is due to the dead outer cells being constantly shed (sloughed off) and replaced by cells from the living epidermal layers below. This process is known as desquamation. Skin consists of an outer epidermis supported by an underlying dermis. It accounts for approximately 15% of the body weight of humans. Magnification: x70 when shortest axis printed at 25 millimetres.(KEYSTONE/SCIENCE PHOTO LIBRARY SPL/DENNIS KUNKEL MICROSCOPY/SCIENCE PHOTO LIBRARY)