A plant gets its mass from the air, more precisely, from carbon dioxide. Carbon dioxide, CO2 (one carbon molecule and two oxygen molecules). Carbon is the basis of all organic substances. DNA, proteins, fats, and carbohydrates are built from it. During photosynthesis—that is, during the formation of organic substances from inorganic ones in plant cells under the influence of light—the plant takes carbon from carbon dioxide and releases oxygen into the environment. Light provides the energy needed to break the bond in a CO2 molecule.