So far, the style has been most prevalent on mid-length strands that hit around the shoulder. From the crown to mid-shaft, the hair is worn smooth and straight, but once you're about two inches from the ends of your hair, the curl flips out. (Or, you can give your curls a dramatic, inward curl that's equally retro, but more on that later.) Celebrity stylists have been partial to the retro flip in the form of half-up half-down ponytails and side-swept bangs.