The Cretaceous Period lasted from about 145 to 66 million years ago and is the final period of the Mesozoic Era. It is known for the dominance of dinosaurs, which roamed the Earth in various forms and sizes. The climate during this time was generally warm, with high sea levels that created shallow inland seas. During the Cretaceous, flowering plants, or angiosperms, began to appear, changing the landscape and providing new food sources for herbivorous dinosaurs. This period ended with a mass extinction event, likely caused by an asteroid impact, leading to the extinction of many species, including the dinosaurs.