Leaves are green because they contain a natural pigment known as Chlorophyll. It is found in both the leaves and the stems. It is found in the structures called Chloroplasts. Chlorophyll takes the energy of sunlight and uses it to convert carbon dioxide and water into chemical energy, in the form of glucose which allows the plant to grow. This process is called Photosynthesis. Chlorophyll does not absorb green light. So, leaves appear green.