Fossils are the preserved remains or traces of ancient organisms, typically found in sedimentary rocks. They can include bones, shells, imprints, or even traces like footprints. Fossils provide valuable information about the history of life on Earth, helping scientists understand how species evolved and how environments changed over time. The process of fossilization usually occurs when an organism is buried quickly after death, protecting it from decay. Over millions of years, minerals in the surrounding sediment can replace organic material, creating a fossil. This process can also preserve the shape and structure of the original organism, allowing researchers to study paleontology and the Earth's biological history.