A fossil is a rock containing the preserved remains of once-living organisms, animals or plants, including footprints or burrows. These remains may have suffered transformations in their composition of form. Paleontology is the science that studies fossils. Most fossils consist of the bones or shells or animals, or the leaves or woody parts of plants. In some marine fossils, shells may be replaced by other minerals, or an impression of the insides of the outsides may be preserved. Fossils are found in sedimentary rocks, especially limestones and shales.

Many of them are the plants and animals now extinct, such as dinosaurs. Fossils reveal important details about the animals and plants that existed millions of years ago.