The Paleogene Period is a geological time frame that lasted from about 66 to 23 million years ago. It follows the Cretaceous Period and is part of the larger Cenozoic Era. This period is characterized by significant changes in climate and the evolution of mammals and birds, which began to diversify after the extinction of the dinosaurs. During the Paleogene, the Earth experienced a warm climate, leading to the development of lush forests and diverse ecosystems. Major groups of mammals, such as primates and whales, began to emerge, setting the stage for the evolution of modern species. The period is divided into three epochs: Paleocene, Eocene, and Oligocene.