Plants use sunlight, water, and carbon dioxide for photosynthesis. In photosynthesis, plants convert light energy into chemical energy, which is stored in glucose molecules. The process of photosynthesis takes place in the chloroplasts of plant cells, which are small organelles that contain chlorophyll. Chlorophyll is a green pigment that absorbs light energy from the sun. The energy from the sun is used to split water molecules into hydrogen and oxygen atoms. The hydrogen atoms are then used to reduce carbon dioxide molecules into glucose molecules. The oxygen atoms are released into the atmosphere.