The primary purpose of photosynthesis is to convert light energy into chemical energy stored in glucose, which plants, algae, and some bacteria use as food. During photosynthesis, these organisms capture sunlight using chlorophyll, a green pigment found in their cells. They combine carbon dioxide from the atmosphere and water absorbed from the soil to produce glucose and oxygen as a byproduct. Photosynthesis is essential for life on Earth, as it provides the foundational energy source for most ecosystems and is responsible for producing the oxygen we breathe. It plays a critical role in regulating atmospheric carbon dioxide levels and supporting the food chain.