A fossil is formed when a prehistoric animal or plant dies and its remains become trapped in soft rock.

This often happened in the mud and sand beneath the ancient seas.

As the sand or silt settled on top of the dead organism, the rocks then formed around the remains of the animal or plant which was then preserved inside the rock.

So, the dead organism left its imprint in the rock.

Strictly speaking, a fossil has to be at least 10,000 years old.

Anything less than 10,000 years old is considered by palaeontologists (the scientists who study fossils) to be young.

So, are you ready to learn all about old fossils?

Let's go!