It started with the Nike Waffle Trainer in 1974. University of Oregon track coach Bill Bowerman ruined his wife’s waffle iron by using it to melt and mold urethane in his mission to invent the best sole pattern for a running shoe. Bowerman was a genius — the little company he co-founded with Phil Knight would become an international behemoth in athletic footwear and apparel — but he forgot to spray that waffle iron with non-stick spray and the urethane glued it shut. From his trial-and-error R&D came the Waffle Trainer, the first widely popular running shoe thanks to the running boom of the late 1970s, when millions flocked to the sport.