What is chlorophyll? What is photosynthesis?

Why are plants green? We take the color for granted in nature, but the green pigment in plant leaves and stems is thanks to a molecule essential for plant life called chlorophyll. Plants use chlorophyll to absorb and harness sunlight energy to power their cell systems and growth. The chemical reactions that convert sunlight energy into forms the plant can store and use are called photosynthesis. These reactions get a lot of work done: they split water molecules into hydrogen and oxygen (yes, the oxygen plants release that we humans and animals need to breathe!), they clean the air by removing carbon dioxide (CO2), and they convert it into a sweet, high-energy molecule enjoyed by plants, humans, and all other kinds of creatures: glucose sugar. So whenever you notice a vibrant green tree, take a deep breath of fresh air, or bite into a juicy fruit, know that you're benefiting from the amazing chlorophyll molecule and the power of the sun!

Image of plant cells containing many chloroplasts, which house the plant's chlorophyll (Image attribution: Kristian Peters)