The fossils became buried under dirt and rock. Heat from the earth and pressure from dirt and rock changes these fossils into oil, natural gas, and coal. One example of a renewable fuel is solar energy. Energy from the sun can be turned into electricity or heat. Another kind of fuel is nuclear energy.
Nuclear energy uses special radioactive materials to make electricity.
Many people believe that nuclear energy is a clean, renewable energy. But making electricity this way leaves behind radioactive wastes that must be stored safely for thousands of years. We use a lot of energy to heat and cool our homes. We burn fuel in our furnaces or boilers for heat. We also burn fuel to heat water for our baths and showers.