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Wheat grain. Coloured scanning electron micrograph (SEM) of a section through a grain (seed) of wheat (Triticum sp.). The majority of the seed comprises a store of starch grains (yellow) surrounded by cell walls (grey). Above this is a layer of cells containing protein (green). The entire seed is covered in a seed coat (brown). The starch provides the embryo plant with the necessary energy for germination. Wheat is an important food crop. The grain is usually ground into flour before being used to make bread and other products. Magnification: x600 when printed 10cm wide. (KEYSTONE/SCIENCE PHOTO LIBRARY/EYE OF SCIENCE)