Photosynthesis is the process by which plants and other organisms use sunlight, carbon dioxide, and water to produce oxygen and energy in the form of glucose or other energy-rich organic compounds. It takes place in two main stages - the light-dependent reactions and the light-independent reactions. The light-dependent reactions use energy from sunlight to produce ATP and NADPH using chlorophyll. The light-independent reactions, also called the Calvin cycle, use ATP and NADPH to fix carbon from carbon dioxide into organic molecules like glucose.