Carbon dioxide (CO2) is the essential gas for photosynthesis, a process utilized by plants, algae, and some bacteria to convert light energy into chemical energy. During photosynthesis, these organisms absorb sunlight using chlorophyll and take in carbon dioxide from the atmosphere through tiny openings called stomata. In the presence of water, light energy drives a series of reactions that transform carbon dioxide and water into glucose, which serves as food for the plants, and releases oxygen into the atmosphere as a byproduct. This process is crucial for life on Earth, as it sustains the food chain and provides oxygen for living organisms.