Did you ever wonder how and why this happens. To answer that question, we first have to understand what leaves are and what they do. Leaves are nature's food factories.
Plants take water from the ground through their roots.
They take a gas called carbon dioxide from the air. Plants use sunlight to turn water and carbon dioxide into glucose. Glucose is a kind of sugar. Plants use glucose as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into sugar is called photosynthesis.