The chemical process that green plants use to make food is called photosynthesis. During photosynthesis, plants convert sunlight, carbon dioxide from the atmosphere, and water from the soil into glucose and oxygen. This process occurs mainly in the chloroplasts of plant cells, where chlorophyll absorbs light energy. Photosynthesis is vital for life on Earth, as it not only provides the food that plants need to grow but also produces oxygen, which is essential for the survival of most living organisms.