Millie Bobby Brown just dropped new styles - and a little jaw, too. The 21-year-old Stranger Things actress showed off her toned abs while giving the first glimpse at one of her latest matching knit two-piece sets from her Florence by Mills Fashion collection. "Just dropped: barre our best-selling collection is back in new shades + styles ," she captioned a series of photos via her brand's official Instagram page on Thursday, September 18.