For thousands of years, humans have believed that there were once flying monsters. They became mythologized, with stories about them shared around the world. But could they have really existed? 220 million years ago dinosaurs were on their rise to dominating Earth. But another group of reptiles was set to make an extraordinary leap: pterosaurs were about to take control of the skies. These creatures were the first flying vertebrates, which grew to have a 40ft wingspan, the size of a jet. The story of how and why these mysterious creatures took to the air is more fantastic that any fiction.