1998–2000: ...Baby One More Time and Oops!... I Did It Again

After Spears returned to the United States, Spears embarked on a shopping mall promotional tour to promote her forthcoming album. Her show was a four song set and she was accompanied by two back up dancers. Her first concert tour followed, as an opening act for 'N Sync.[20] Her debut album, ...Baby One More Time, was released on January 1999. It debuted at number one on the U.S. Billboard 200 and was certified two-times platinum by the Recording Industry Association of America after a month. Worldwide, the album topped the charts in fifteen countries and sold over ten million copies in a year.[21] It became the biggest selling album ever by a teenage artist.[14] The title track was released as the lead single from the album. Originally, Jive Records wanted its music video to be animated; however, Spears rejected it, and suggested the final idea of a Catholic schoolgirl.[19] The single sold 500,000 copies on its first day, and peaked at number one on the Billboard Hot 100, topping the chart for two consecutive weeks.[22][23] "...Baby One More Time" later received a Grammy nomination for Best Female Pop Vocal Performance.[24] The title track also topped the singles chart for two weeks in the United Kingdom, and became the fastest-selling single ever by a female artist, shipping over 460,000 copies.[25] It would later become the 25th most successful song of all time in British chart history.[26] Spears is also the youngest female artist to have a million seller in the country.[27] "(You Drive Me) Crazy" was released as the third single from the album. It became a top-ten hit worldwide and propelled ...Baby One More Time to sell 26 million copies.[28] The April 1999 cover of Rolling Stone featured Spears laying on her bed, clad with a bra, shorts and an open top. The American Family Association (AFA) referred to the shoot as "a disturbing mix of childhood innocence and adult sexuality" and called to "God-loving Americans to boycott stores selling Britney's albums." Spears responded to the outcry commenting, "What's the big deal? I have strong morals. [...] I'd do it again. I thought the pictures were fine. And I was tired of being compared to Debbie Gibson and all of this bubblegum pop all the time."[29] Shortly before, Spears had announced publicly she would remain a virgin until marriage.[14]
On June 28, 1999, Spears began her first headlining ...Baby One More Time Tour in North America, which was positively received by critics,[30] but generated some controversy due to her racy outfits.[31] An extension of the tour, titled Crazy 2k, followed in March 2000. Spears premiered songs from her upcoming second album during the show.[17] Oops!... I Did It Again, her second studio album, was released in May 2000. It debuted at number one in the US, selling 1,3 million copies, breaking the SoundScan record for the highest debut sales by any solo artist.[32] The album sold over 20 million copies worldwide.[33] Rob Sheffield of Rolling Stone said that "the great thing about Oops! – under the cheese surface, Britney's demand for satisfaction is complex, fierce and downright scary, making her a true child of rock & roll tradition."[34] The album's lead single, "Oops!... I Did It Again", peaked at the top of the charts in Australia, New Zealand, the United Kingdom and many other European nations.[27][35] The album as well as the title track received Grammy nominations for Best Pop Vocal Album and Best Female Pop Vocal Performance, respectively.[36] The same year, Spears embarked on the Oops!... I Did It Again World Tour, which grossed $40.5 million; she also released her first book, Britney Spears' Heart-to-Heart, co-written with her mother.[14][37] On September 7, 2000, Spears performed at the 2000 MTV Video Music Awards. Halfway through the performance, she ripped of her black suit to reveal a sequined flesh-colored bodysuit, followed by heavy dance routine. It is noted by critics as the moment that Spears showed signs of becoming a more provocative performer.[38] Amidst media speculation, Spears confirmed she was dating 'N Sync member Justin Timberlake.[14]