Geometric and structural, a box bag is a need-to-have accessory. Typically formed in the shape of a rectangle or square, it reappears in different colors and leather each season. Made with graphic lines and attention-to-detail, a box bag can be sleek or statement-making. Versions from Dolce & Gabbana are often bright and heavily embellished, Lanvin's snakeskin box bags are crafted from rich-hued leather and color-blocked panels appear throughout Derek Lam's offering. For the ultimate box bag, look to Sophie Hulme's collection of totes, cross-body and shoulder bags.