The process by which plants release oxygen is called photosynthesis. In this process, plants use sunlight, carbon dioxide, and water to produce glucose and oxygen. During photosynthesis, chlorophyll within the plant cells captures sunlight, converting light energy into chemical energy. This energy facilitates the conversion of carbon dioxide absorbed from the atmosphere and water absorbed from the soil into glucose, which serves as food for the plant. The by-product of this process is oxygen, which is released back into the atmosphere, playing a vital role in sustaining life on Earth by providing oxygen for animals and humans.