Hold up a bottle of vegetable oil. Vegetable oil and animal oil have played an important role in human history. Vegetable oils, like olive oil, corn oil or safflower oil, are often used in cooking. Animal oil, like that from whales, seals and livestock, was used in the past for lighting lamps as well as for waterproofing. Hold up a piece of firewood.
Wood comes from trees, which are, of course, plants.
The plants got their energy from the sun. When trees are cut down and burned, they release their energy in the form of heat. Many homes are heated with wood-burning stoves. The following three energy sources come from prehistoric fossils. Like the methods described above, ancient plants absorbed the energy from the sun and converted it into more plants.