To what does Mary-Kate Olsen chalk up the success of The Row, the three-year-old design label she runs with her sister Ashley? "It's about the fabrics, the fit, and how the clothes feel on the body," she said at a showroom presentation today, where she was hands-on, helping the models into highlights from their Resort collection. In keeping with the Fall runway debut, their latest effort is quite understated, but not without delightful little details. An otherwise spare white silk three-quarter-sleeve minidress, for instance, has subtle slice pockets at the top of the thighs, the better to help you ace your slouch. The pants of a tweedy blue cashmere suit, meanwhile, feature a crossover waistband that ensures the silhouette is more feminine than masculine. And replacing the denim-colored python dress that had everyone talking in February is a black matte crocodile vest. Accessorizing all the looks: a great old pair of loafers from the minimal nineties (not one of the Olsens' own designs, but still testament to their discerning taste). And if shoes aren't in The Row's near future, Mary-Kate did say that they're working on a prototype for their first bag.