A process that occurs in plants, algae and bacteria that transforms sunlight into sugar which is then converted into ATP–a “biological fuel” used by all living things. Photosynthesis involves converting carbon dioxide in the air into sugars needed by the plants. Oxygen is released back into the atmosphere as a byproduct of photosynthesis. The process not only helps plants generate food for themselves, it also plays a role in maintaining good air quality–reducing the amount of carbon dioxide while producing oxygen.