Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process occurs in two stages: Light-dependent reactions: These take place in the thylakoid membranes of chloroplasts and involve the absorption of light energy by chlorophyll. Water molecules are split, releasing oxygen, and the energy is used to produce ATP and NADPH. Calvin Cycle: This occurs in the stroma of the chloroplast and does not require light. ATP and NADPH from the light-dependent reactions are used to convert carbon dioxide into glucose. Photosynthesis is critical for life on Earth because it is the primary source of energy for nearly all living organisms. It also produces oxygen, which is essential for respiration.