Dinosaurs ruled the world for roughly 140 million years—until they suddenly disappeared. While decades of research point to an asteroid impact at Chicxulub crater as the end of the dinosaurs’ reign 66 million years ago, scientists weren’t always so sure what happened to these mesmerizing creatures. Theories varied wildly throughout the twentieth century as the field of paleontology grew, but it wasn’t until the 1980s that one theory emerged as a major breakthrough in the extinction mystery. Today’s scientists continue to piece together the puzzle with discoveries that give us a clearer picture of what happened to the dinosaurs.