The Mesozoic Era is a geological time period that lasted from about 252 to 66 million years ago. It is often called the "Age of Reptiles" because it was dominated by dinosaurs, which evolved and thrived during this time. The era is divided into three periods: Triassic, Jurassic, and Cretaceous, each marked by significant developments in Earth's climate, geography, and life forms. During the Mesozoic Era, the continents were arranged differently than today, forming a supercontinent called Pangaea. This era saw the emergence of many new species, including the first birds and mammals. The Mesozoic ended with a mass extinction event, likely caused by an asteroid impact, which led to the decline of dinosaurs and paved the way for the rise of mammals in the following Cenozoic Era.