A fossil is the preserved remains or traces of ancient living organisms, such as plants, animals, or microorganisms. Fossils can form in various ways, including through mineralization, where minerals replace organic material, or by being trapped in sediment. They provide valuable information about the Earth's history and the evolution of life. Fossils are typically found in sedimentary rocks, which form from layers of sediment over time. Common types of fossils include dinosaur bones, leaf impressions, and shells. Scientists study fossils to understand past environments, climate changes, and how species have adapted or gone extinct over millions of years.