Plants use a process called photosynthesis to make food. During photosynthesis, plants trap light energy with their leaves. Plants use the energy of the sun to change water and carbon dioxide into a sugar called glucose. Glucose is used by plants for energy and to make other substances like cellulose and starch. Cellulose is used in building cell walls. Starch is stored in seeds and other plant parts as a food source.

Source: Nature Works