Fossils are the preserved remains or traces of organisms from an earlier geological period. They provide direct physical evidence of past life, allowing scientists to reconstruct ancient ecosystems, biodiversity, and evolutionary relationships. Formation typically requires the rapid burial of organic material in sediment, followed by processes such as mineralization, permineralization, or carbonization, which replace the original biological structures with inorganic compounds. The study of fossils, known as paleontology, is foundational to geology and biology, offering critical data regarding the planet's deep history, the changing climate, and the morphological adaptations of life forms over vast stretches of time.