The process that plants use to release oxygen into the atmosphere is called photosynthesis. During this process, plants convert carbon dioxide and water into glucose and oxygen, using sunlight as an energy source. Chlorophyll, the green pigment in plant cells, captures light energy, driving the chemical reactions necessary for photosynthesis. This essential biological process not only provides energy for the plants themselves but also significantly contributes to the Earth's oxygen supply, supporting life for various species, including humans. Photosynthesis plays a crucial role in the global carbon cycle.