Long before history was ever recorded, fascinating creatures swam in oceans, soared through skies, and roamed across terrains very different from those of Earth today. Humans have never laid eyes on these creatures, so how do we know about them? How did they come to be, and why are they not around today? What was Earth like millions and even billions of years ago? From the first microscopic single-celled organisms to the largest whales alive today, life has been emerging, flourishing, and dying out on Earth for nearly four billion years. Discover how fossils are the keys to unlocking our understanding of prehistoric life. Learn about many species of dinosaurs and pterosaurs, some of the most prolific and impressive creatures to ever exist on Earth. Find out how fossils form, make models of your own, and examine a real fossil. Delve into the geologic ages of Earth and uncover the creatures that defined them. The 32-page book guides your experiments and discoveries. Activities include: assemble a dinosaur skeleton, build a pterosaur mobile, cast plaster fossils, play a dinosaur quiz game, create a time spiral, make a geologic time bookmark.