Almost all of the energy that the living organisms use comes from the energy of the Sun. The plants are called primary producers because of their ability to transform the energy that comes from the Sun into chemical energy. They are able to do this with the help of the pigment system in their cells that transfers the energy from the Sun into organic molecules. This energy is then moved trough the food chain. So, when we eat a plant or an animal, we are actually consuming energy that has originated from the Sun.