Scanning electron micrograph of a single pollen grain from a blue anemone flower. Pollen grains contain the male gamete and are produced in the anther. They are transferred from one flower to another (pollination) so that fertilization of the female gametes can occur (sexual plant reproduction). Pollen is a common trigger of hay fever or seasonal allergies. Pollen grain size is 22 micron across. Supplied by Kevin Mackenzie, courtesy of Wellcome Images.