How are fossils made?

Now we know what fossils are, but how are they made?

It can take millions of years for a fossil to form.
When a living thing dies, it must be covered with dirt or mud to make a fossil.
Thousands and millions of years pass.
More and more layers of dirt and mud cover the dirt and mud with the plant or animal in it.
The pressure from these new layers causes the lower layers to slowly turn into rock.
That rock is a fossil.