To photosynthesize means to make food from sunlight, water, and carbon dioxide. This is what plants do to survive and grow. Inside their leaves, plants capture energy from the sun and use it to transform water from their roots and carbon dioxide from the air into sugar, which feeds the plant. As a bonus, they release oxygen into the air, which is what we breathe.

When you see a plant growing tall and green in a sunny window, you're watching photosynthesis in action. The green color comes from chlorophyll, a substance in the leaves that captures sunlight and makes the whole process possible.

Trees, grass, algae, and even some bacteria can photosynthesize. Without photosynthesis, there would be no plants, far less oxygen in our atmosphere, and very little food for animals or humans. Every time you eat a salad, a piece of fruit, or even a burger (since cows eat plants), you're benefiting from photosynthesis. Scientists estimate that photosynthesizing organisms produce hundreds of billions of tons of oxygen every year, while also removing carbon dioxide from the atmosphere. In a real sense, photosynthesis helps make Earth a planet where animals like us can live.