Pollination describes the transfer of pollen to the stigma of the carpel of a flower, whereby the male gametes are contained in the pollen formed in the stamens. A distinction is made between self-pollination and cross-pollination: while in self-pollination the pollen comes from the same flower, cross-pollination takes place using pollen from another flower of the same plant species. Bees play a central role here, as they transfer the pollen from flower to flower and thus enable fertilization.