Dinosaurs were a group of reptiles that lived millions of years ago, long before humans existed. They roamed the Earth during the Mesozoic Era, which is often called the "Age of Dinosaurs." Some dinosaurs were huge, like the Brachiosaurus, while others were small and fast, like the Velociraptor. They came in many shapes and sizes, and some even had feathers! Dinosaurs are fascinating because they were the dominant land animals for over 160 million years. They eventually went extinct about 65 million years ago, likely due to a massive asteroid impact or volcanic activity. Today, scientists study dinosaur fossils to learn more about these incredible creatures and their world.