Pollen is a powder like substance containing gametophytes of plants. These produce sperm cells during pollination. Pollen grains have an outer layer that protects the sperm cells after they get trapped on a stamen and travel to the pistil of a seed plant. When pollination is occurring the pollen grain forms a pollen tube that leads the sperm to an ovule. The picture above is of a flower that uses pollen for pollination.