Fossil fuels such as coal, oil, and natural gas are natural resources that were formed over millions of years from the remains of ancient plants and animals. Coal forms from decayed plant matter that is buried and undergoes heating and pressure over time. Oil and natural gas similarly form from the remains of sea creatures buried deep underground. These fossil fuels are important sources of energy that are extracted and refined to produce many everyday products like gasoline, plastics, and electricity. However, accidents like oil spills can cause significant environmental damage.