Pollen is a fine powder produced by flowering plants, including trees, grasses, and flowers. It contains the male gametes necessary for fertilization and is essential for plant reproduction. When pollen is transferred from the male part of a flower to the female part, it can lead to the formation of seeds. Pollen is also a significant factor in ecosystems, as it helps in the production of fruits and seeds that many animals rely on for food. Additionally, it can be a common allergen for humans, causing seasonal allergies known as hay fever when inhaled in large quantities.