Illustration of the process of photosynthesis, showing sunlight shining of the surface of leaves of Fagus sylvatica, the common or European beech. Photosynthesis involves the action of sunlight on the green pigment chlorophyll to provide energy necessary for the synthesis of carbohydrates from carbon dioxide and water. This type of nutrition is known as autotrophic; animal nutrition, where energy is derived from an external supply of food, is termed heterotrophic.