The Ford Mustang continues to be America's most recognizable sports car, and one of its most long-running. But it's about to undergo its biggest transformation yet with the upcoming all-electric Mustang Mach-E. So how did we get from a cute little pony car to a high-powered EV? We break down all the changes and innovations the Ford Mustang has undergone in its 56 years that have made it so iconic.