 Spears became an international pop culture icon immediately after launching her recording career . Rolling Stone magazine wrote : " One of the most controversial and successful female vocalists of the 21st century , " she " spearheaded the rise of post @-@ millennial teen pop ... Spears early on cultivated a mixture of innocence and experience that broke the bank " . She is listed by the Guinness World Records as having the " Best @-@ selling album by a teenage solo artist " . Melissa Ruggieri of the Richmond Times @-@ Dispatch reported , " She 's also marked for being the best @-@ selling teenage artist . Before she turned 20 in 2001 , Spears sold more than 30 million albums worldwide " . Barbara Ellen of The Observer has reported : " Spears is famously one of the ' oldest ' teenagers pop has ever produced , almost middle aged in terms of focus and determination . Many 19 @-@ year @-@ olds haven 't even started working by that age , whereas Britney , a former Mouseketeer , was that most unusual and volatile of American phenomena — a child with a full @-@ time career . While other little girls were putting posters on their walls , Britney was wanting to be the poster on the wall . Whereas other children develop at their own pace , Britney was developing at a pace set by the ferociously competitive American entertainment industry " . ... Baby One More Time is Spears ' most successful album to date , with worldwide sales over 30 million copies , and also the best @-@ selling album by a teenage solo artist . 
