Botanists study various aspects of plants. For example, they may study their physiological processes such as photosynthesis at the molecular level, the evolutionary history and relationships of plants, or their current relationships with their environments. they may focus on the agricultural applications of plants used for food, fiber, fuel, turf, and cover crops, studying their responses to stresses from pests, disease, and climate variations. They may also work on plant breeding to develop hardier strains.