The main source of energy for the processes of photosynthesis is sunlight. In this process, chlorophyll in plant cells captures sunlight and converts it into chemical energy. This energy, along with carbon dioxide and water, is used to produce glucose and oxygen. Photosynthesis is essential for life on Earth, as it forms the foundation of most food chains and provides the oxygen necessary for aerobic organisms. It also plays a crucial role in regulating atmospheric carbon dioxide levels.