The energy required for photosynthesis comes from the sun as light energy; plants transform this light energy into chemical energy, or sugars. Plants perform this energy conversion using light, water, carbon dioxide and a green substance called chlorophyll. Photosynthesis takes place in a plant's leaves.
Sunlight includes the full range of colors in the light spectrum. The chlorophyll in plants absorbs the red and some of the blue light waves for use in photosynthesis, and the light waves that are not absorbed are reflected back, giving plants their green color. Another waste product of photosynthesis is oxygen, making plants crucial to the survival of humans.