What is a fossil?
organisms have lived on earth for at least 3.5 billions years. during that time, organisms and the environment have changed many times. fossils hold clues to those changes. fossils are the remains or traces of organisms that lived long ago.
How are fossils formed?
most fossils are found in sedimentary rock. the original organisms were trapped in sediments. when the sediments hardened into rock, signs of the organisms stayed in the rock.