Energy sources are the means by which energy is produced and used. ATOMS, FUELS, BATTERIES, nutrients, electric cells, and the power that be are all examples of energy sources. ATOMS are the smallest particles of matter and can be used to generate energy through nuclear fission or fusion. FUELS are substances that can be burned to produce energy, such as coal, oil, and natural gas. BATTERIES are devices that store energy and can be used to power electrical devices. Nutrients are substances that provide energy to living organisms, such as carbohydrates, proteins, and fats. Electric cells are devices that convert chemical energy into electrical energy. The power that be refers to those who have the authority to make decisions about energy production and use.