The process by which plants convert carbon dioxide and water into food via sunlight is called photosynthesis, which comes from the Latin words for "formation in light." All our food comes from this process, either directly or indirectly. We eat green plants and their grains and fruits as well as the animals that feed on such plants.

It took scientists hundreds of years to understand what happens during photosynthesis. In this process, sunlight stimulates the chlorophyll found in structures in green plants called chloroplasts. In the chloroplasts, the sunlight reacts with carbon dioxide that the plant breathes in through microscopic holes in its leaves called stomata and with water that it absorbs through its roots. During a series of light and dark reactions, the water molecules are broken down into hydrogen and oxygen, and the hydrogen combines with carbon dioxide to produce glucose, a simple sugar that is...