Fossils are the preserved remains or traces of a living organism, plant or animal. They tell us what life on Earth was like hundreds, thousands or even millions of years ago!
This is the fossil of a creature called an ammonite. Ammonites were squid-like creatures that lived in the sea 400 million to 65 million years ago.
Paleontologists and archaeologists are scientists who dig up the ground to find fossils. When they dug in the Himalayas, they found lots of ammonites. But how did the fossils of sea creatures end up on the tallest mountains in the world?
To answer this question, we have to go back a hundred million years, when the Earth was quite different. Back then, Earth had only two enormous continents: Gondwanaland and Laurasia. Between them was the gigantic Tethys Sea.
Just beneath the surface of the continents and the sea sits a layer of Earth called the outer crust. This outer crust is made of very large moving pieces called plates. Earth's plates are almost 100 kilometres thick and made of solid rock. But underneath is a layer of molten rock that allows the plates on top to move really slowly.

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