How do we know huge dinosaurs existed hundreds of millions of years ago? After all, no humans were around to see them. And how are scientists able to figure out what the Earth looked like during different periods of its vast history? The answers to these questions, and many more, can be found in a trail of natural clues called fossils that the Earth and its creatures left behind, usually buried in rocks or beneath the ground. WHAT FOSSILS TELL US: THE HISTORY OF LIFE examines the ever-unfolding stories these fossils reveal about life on Earth. Dig in and learn how fossils were formed, and find out about some of the most important people and places in the field of paleontology.