The process of plants releasing oxygen is called photosynthesis. During photosynthesis, plants convert carbon dioxide from the atmosphere and sunlight into glucose and oxygen, which is released as a byproduct. This process predominantly takes place in the chloroplasts of plant cells, where chlorophyll captures sunlight. Photosynthesis is essential for life on Earth, as it not only provides oxygen necessary for most living organisms but also serves as the foundation of the food chain. Overall, photosynthesis is crucial in regulating atmospheric gases and supporting ecosystems worldwide.