Fossils are the remains of animals or plants that lived a long time ago.When we think of fossils, the first things that come to mind are the bones of dinosaurs; but a fossil can be anything.

Though there is no one age, a good rule is anything over 10,000 years old can be considered a fossil.

The oldest fossils ever discovered are more than 3.5 billion years old.

Fossils are found all over the world and on every continent.

A paleontologist is a scientist that studies fossils.

Types of Fossils There are two main types of fossils: body fossils and trace fossils.

A body fossil is the physical remains of an animal. Some very small organisms, called microbacteria, leave behind microscopic particles called filaments.Trace fossils are not the remains of an animal, but something that shows how it lived or died.Footprints, tools, or plant matter are different types of trace fossils.The two fossil categories can be broken down further.A cast fossil is a fossil made when an organism that is buried in sediment decays and leave behind a mold, or hollow impression in its shape.A cast fossil is like a mold fossil, but in the case of a cast fossil the mold has been filled with minerals.