As one of the biggest pop icons in the last two decades, Britney Spears's most famous fashion moments are hard to forget. From her early days opening for 'N Sync, Britney championed crop tops, spaghetti-strap dresses, and outfits that read more sporty girl next door than sexy. After the release of her schoolgirl-inspired music video for "...Baby One More Time," the singer's image became more provocative: Hemlines grew shorter, necklines went lower, and she appeared in only underwear on a controversial Rolling Stone cover. After that, Britney brought us what are some of the most memorable outfits in pop-princess history, including the "Oops! I Did Again" red latex body suit, a matching all-jean getup with then-boyfriend Justin Timberlake, and a sparkly nude bra-and-pants number during a VMA performance, which seemed incredibly racy at the time. In honor of her birthday today, take a look back at Britney Spears's fashion transformation from teen star to the present.