The main purpose of photosynthesis is to convert light energy, usually from the sun, into chemical energy stored in glucose, a type of sugar. This process occurs primarily in plants, algae, and some bacteria, allowing them to produce their own food. During photosynthesis, these organisms utilize carbon dioxide from the atmosphere and water absorbed through their roots, releasing oxygen as a byproduct. Photosynthesis is essential for life on Earth, as it forms the basis of the food chain and contributes to the oxygen content of the atmosphere, supporting aerobic life forms.