It's Britney Spears' 32nd birthday today! It's so hard to believe that the Princess of Pop is all grown up and in her 30s — can you believe that "...Baby One More Time" was released 15 years ago? Through the ups and downs, good times and bad, we've always been fans of this all-American beauty. To celebrate her birthday, we're taking a retrospective squiz at Miss Spears' changing hair and makeup looks over the past 14 years. We've got everything from some of her first pics, in 1999, to that Rolling Stone cover, those double denim days with JT (sorry Brit, we couldn't resist) to her brunette days, right up until a few weeks ago. Click through to see all the incredible pictures, and happy birthday Britney!