Definition: Fossilisation, also known as fossilization, is a process in which organic materials undergo significant changes to become non-organic. This can occur through various means such as heat, pressure, or chemical reactions. The result of this process is that the material becomes more and more fossilized, with its original structure becoming less visible. Fossils are often found on rocks, bones, and other dead organisms, and they provide valuable insights into the history and evolution of life on Earth.