The Kellogg Co. is testing new boxes for its iconic corn flakes. The six-month test market in Detroit will gauge acceptance of the boxes, which hold the same amount of Kellogg's Corn Flakes as existing cartons but come in a nearly square shape. The new boxes use space more efficiently both on store shelves and in consumers' pantries, while reducing material use by about 8%. This marks the most significant innovation in Kellogg's mainstream cereal boxes since the 1950s, according to a company statement.