From baseball caps to saris to the little black dress, there's a social history woven into the clothing we wear. A new exhibition at New York's Museum of Modern Art (MoMA) explores that history.

Now ubiquitous in fashion circles, double-breasted blazers can read super formal when buttoned. To render yours cooler, breezier and more modern, let it flop open like a devil-may-care cardigan—and ...