Though they trace as far back as the 14th century, leggings first became really popular back in the late 1950s, when chemist Joseph Shivers created the first Lycra pair. Come the '80s, leggings got a little more edgy, like the shiny black pair that Olivia Newton-John wears with a moto jacket in Grease. A couple of clips later, the celebrity product sightings continue when a lineup of...