Learn how fossils provide information about the history of today’s organisms with this video from NOVA’s Evolution Lab. The remains of some species are preserved in fossils, which are clues in rock about many of the creatures that once roamed our planet. These fossils often share features with living species, and the similarities provide insight into how organisms have changed over time. The fossil record shows evidence of gradual change, including the existence of transitional organisms. However, fossils cannot provide a complete account of evolution because not all species have been preserved as fossils.