All living organisms need energy to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is the set of life-sustaining chemical processes that enables organisms transform the chemical energy stored in molecules into energy that can be used for cellular processes. Food provides animals with the materials and energy they need for body repair, growth, warmth, and motion. Plants acquire material for growth chiefly from air, water, and process matter and obtain energy from sunlight, which is used to maintain conditions necessary for survival. Animals drink and eat food to obtain the matter and energy they need for their life processes. Some organisms, such as plants, can make their own food. An organism that makes its own food is called a producer. Plants are able to use the energy from sunlight to produce sugars, which are a source of energy and matter. Food is composed of molecules that serve as fuel and building material for all organisms as energy stored in the molecules is released and used. The breakdown of food molecules enables cells to store energy in new molecules that are used to carry out the many functions of the cell and thus the organism. Like energy, matter in the Earth system cycles within and among Earth's spheres: the atmosphere, geosphere, hydrosphere, biosphere, and even the anthrosphere. Dead producers and consumers and their waste products provide matter and energy to decomposers. Decomposers transform matter back into inorganic forms that can be recycled within the ecosystem. So, the energy that enters an ecosystem as sunlight eventually flows out of the ecosystem in the form of heat.Energy from the Sun is the driver of many Earth System processes. This energy flows into the Atmosphere and heats this system up It also heats up the Hydrosphere and the land surface of the Geosphere, and fuels many processes in the Biosphere.