Fossils are the preserved remains or traces of ancient organisms that lived in the past and are preserved in rocks. They provide a window into the distant past, revealing how life has changed across vast periods of Earths history. Fossils can teach us where life and humans came from, show us how the Earth and our environment have changed through geological time, and how continents, now widely separated, were once connected. They can also provide important evidence for evolution and the adaptation of plants and animals to their environments. By examining the physical characteristics of the fossils, we may infer their original size, shape, method of locomotion, diet, and even behavior and ecological relations with other organisms and the environment in which they lived. Fossils can also reveal ecological relationships from the past. They can be used to determine the relative age of two or more layers of rock, or strata, that are in different places within the same country or somewhere else in the world. Fossils can be used to recreate different worlds like worlds populated by dinosaurs or dragonflies with a two-meter wingspan.