Large intestine. Coloured transmission electron micrograph (TEM) of a section through the wall of the large intestine. The surface consists of many small hair-like absorptive cells (green). These absorb water from the digested food that passes through the lumen (internal space, white). The surface of the large intestine needs lubrication, and this is provided by goblet cells (orange), which produce mucus. Magnification: ×210 when printed 10cm high. Cover credit: BIOMEDICAL IMAGING UNIT, SOUTHAMPTON GENERAL HOSPITAL/SCIENCE PHOTO LIBRARY.