First lady Michelle Obama celebrated her husband’s inauguration Tuesday night wearing a white chiffon, one-shoulder gown covered in fluffy appliques and beading that will now become part of fashion history.

Designed by 26-year-old Jason Wu, much loved in the fashion world but otherwise not well known, the gathered-skirt gown was surprising for its reserve given Michelle Obama’s love of jewel tones and sleek silhouettes. Yet it was unconventional, too, exposing her much-remarked-upon, well-toned arms.

The gown’s slight train swirled pleasingly and her shoulder-sweeping earrings picked up the gown’s sparkle as she and President Barack Obama danced the evening’s first dance at the Neighborhood Ball at Washington’s Convention Center.