Velour in the winter. Terrycloth in the summer. The coolest, most popular young women of the early aughts had a rainbow of Juicy Couture tracksuits lined up in their closets. Britney Spears wore them while she shopped and sipped Starbucks, Mariah Carey wore them with heels in airports, Paris Hilton and Nicole Richie wore them on The Simple Life, and even Kim Kardashian wore them while strolling down Rodeo Drive in flip-flops and holding a gigantic metallic Louis Vuitton bag. In the mid-2000s, they were the height of luxury and as ubiquitous as body glitter.