Muskoxen are built to chill. These animals can endure, even thrive, in some of the harshest conditions on Earth—the Arctic winter. Their long, wiry outer coat covers a soft and thick inner layer, called qiviut, that keeps them toasty even as temperatures plummet. When winter ends, the muskoxen shed this undercoat, which is collected and spun into yarn that"s warmer than sheep"s wool and softer than cashmere—pricier, too.