Chlorophyll’s job in a plant is to absorb light—usually sunlight. The energy absorbed from light is transferred to two kinds of energy-storing molecules. Through photosynthesis, the plant uses the stored energy to convert carbon dioxide (absorbed from the air) and water into glucose, a type of sugar. Plants use glucose together with nutrients taken from the soil to make new leaves and other plant parts. The process of photosynthesis produces oxygen, which is released by the plant into the air.

Chlorophyll gives plants their green color because it does not absorb the green wavelengths of white light. That particular light wavelength is reflected from the plant, so it appears green.

Plants that use photosynthesis to make their own food are called autotrophs. Animals that eat plants or other animals are called heterotrophs. Because food webs in every type of ecosystem, from terrestrial to marine, begin with photosynthesis, chlorophyll can be considered a foundation for all life on Earth.