The main process plants use to convert sunlight into energy is photosynthesis. During photosynthesis, plants absorb carbon dioxide from the atmosphere and water from the soil. Using sunlight as an energy source, they convert these raw materials into glucose and oxygen. The glucose serves as energy and a building block for growth, while the oxygen is released as a byproduct. This process is fundamental to life on Earth, as it produces oxygen and forms the basis of the food chain.