Britney Spears is the defining figure of the Y2K pop era, the artist who shaped the sound and look of pop music in the first decade of the 21st century. Like Madonna before her, Spears melded her music to her image so thoroughly, it became impossible to separate the two: the title of "...Baby One More Time," her 1999 breakthrough hit, evokes the industrial Max Martin-produced hook and Spears' schoolgirl dance routine in equal measure. "...Baby One More Time" arrived in early 1999, months after the launch of MTV's Total Request Live and just as the pop charts were shaking off post-alternative doldrums in preparation for millennial bacchanalia that was just around the corner. Spears provided the soundtrack for that era as she moved from fizzy bubblegum like "(You Drive Me) Crazy" to the slinkier, sexier funk of "I'm a Slave 4 U."