The Mesozoic ERA, also known as the Age of Reptiles, was a period of time lasting from about 252 million to 66 million years ago. It is divided into three periods: Triassic, Jurassic, and Cretaceous. During this ERA, the Earth saw the rise of dinosaurs, the first birds, and the first flowering plants. The Mesozoic ERA is sometimes referred to as the 'Middle Life' because it followed the Paleozoic ERA and preceded the Cenozoic ERA.