The monarch butterfly migration is one of nature’s greatest events. This orange-winged wonder travels up to 4,500 km from all over North America to spend the winter hanging from oyamel fir trees in central Mexico’s mountain forests. I got to go there. Seeing tens of millions of butterflies dangling from the treetops is a truly breathtaking sight. But how does an animal with a brain the size of a poppy seed navigate to this one special place, especially since the last monarchs to make the trip lived 4 or 5 generations earlier? Get ready for an amazing story of science, instinct, and navigation.