Billons of animals and plants die every day. Almost all of them decay through natural processes back into the elements that their bodies were made of. Of course, after they break down, they don't look like the things they once were. But a very small number of them will die in just the right environment to preserve their bodies, or at least the shape of their bodies. These are called fossils, and they can last a very long time - even millions of years. The most likely things to become fossilized are the hard parts of organisms such as bones, teeth and shells. Soft parts like flesh and hair are easily broken down, so we have almost no evidence...
