Sienna Miller knows how to start (and own) a trend — boho chic, anyone? — but her latest turn toward a more feminine fit-and-flare silhouette is something she has actually loved for years. While Miller's long-sleeved, light blue Matthew Williamson box-pleat dress may be the most recent example of her penchant for the girlier style, she has also stepped out in Topshop, Valentino, and Twenty8Twelve iterations. And it's not hard to see why she loves a fit-and-flare dress — and why, if you haven't converted yet, it's a really flattering choice for most body types. By cinching the smallest part of your waist and letting the skirt flare out over the hips, it creates an illusion of a bombshell-like figure. And for those of you who aren't after a totally body-con fit, this route touches on something halfway to formfitting. All the proof you need, according to Sienna Miller, is right here.