Yellow chamomile pollen grains. Coloured scanning electron micrograph (SEM) of pollen grains from a yellow chamomile (Cota tinctoria) flower, showing their highly sculpted outer wall (exine), which may assist in their dispersal. Pollen grains are the male sex cells of a flowering plant. Their characteristic surface is used by botanists to recognise and classify plants. Magnification: x670 when printed at 10 centimetres wide.