The process by which plants release oxygen is called photosynthesis. During photosynthesis, plants use sunlight, carbon dioxide from the air, and water from the soil to produce glucose (a form of sugar) and oxygen. This process takes place primarily in the chloroplasts of plant cells, where chlorophyll (the green pigment) captures light energy. The overall reaction can be summarized as: carbon dioxide + water + light energy → glucose + oxygen. Photosynthesis is vital for life on Earth, as it not only provides oxygen for humans and animals to breathe but also serves as the foundation for the planet's food chains.