Photosynthesis, you might remember, is the process in which plants convert light energy from the sun to chemical food energy. Brightly colored pigments in leaves are essential to the first steps of light absorption, with chlorophyll being the most important pigment. There are two main types of chlorophyll: chlorophyll A, which is bluish-green, and chlorophyll B, which is yellowish-green. During most of the growing season, leaves contain more chlorophyll than any other pigment, making them appear green. In the fall, however, chlorophyll begins to break down, and the other pigments, which have been there all along, are finally revealed: we see pretty yellow and orange fall leaves. The yellow pigments in leaves are called xanthophylls, and the orange pigments are called carotenoids (carotenoids are easy to remember because they are orange like a carrot!).