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Blood clot, SEM. Coloured scanning electron micrograph (SEM) looking down on a surface of the small intestine. This is the internal surface that secretes digestive fluids and absorbs nutrients from digested food. It is heavily folded, forming these projections called villi. This folding increases the surface area available for absorption. This is the ileum, the last part of the small intestine. Yellow goblet cells are interspersed within the mainly absorbtive epithelium. Magnification: x300 when printed at 10 centimetres across. (KEYSTONE/SCIENCE PHOTO LIBRARY/STEVE GSCHMEISSNER)