Angiosperms (flowering plants) require pollinators to transfer pollen to the pistil where fertilization occurs. Many plants have specific features that attract some insects, whereas these insect species have particular adaptations for the pollination of the species. As a result, it is suggested that plants and their pollinators co-evolved (evolved together) and acquired their features during the years of evolution, depending on each other. For example, bees prefer yellow or blue flowers with bilateral symmetry. At the same time, flowers made selective pressure on bees with specific body shape, hairiness, and efficient pollen-transferring behavior. As a result, during the co-evolution, different specializations created particular relationships that are beneficial for both species.