7) 'Womanizer'

Even though critics proclaimed the song as just a "comeback single" with 'Toxic' similarities, the song still reached No.1 on the Billboard Hot 100, which Spears hadn't done since '...Baby One More Time.'

6) '...Baby One More Time'

Britney Spears' debut single still remains her most successful, reaching No. 1 in every chart it was featured in (and in every country it charted in). By seventeen, Spears had won Teen Choice Awards' 'Single of the Year,' MTV Europe Music Awards' 'Best Song,' and was nominated a Grammy Award for 'Best Female Pop Vocal Performance' for this tune. And she somehow made the school girl outfit and pink pom-pom hair-ties trendy again, worn by every tween in the succeeding years.

5) 'Toxic'

With obvious metaphorical references comparing love to a toxic drug, 'Toxic' was her fourth top 10 single in the U.S., reached No. 1 in the UK and Australia and in 2005 won the Grammy Award for 'Best Dance Recording.' Bet Kylie Minogue wishes she hadn't turned down the offer to include this song in her ninth studio album, 'Body Language.'

4) 'Everytime'

Written by Spears and her background vocalist Annette Artani, the piano-led ballad with string instruments is entirely different than the rest of her dance-pop singles on 'In the Zone'; the lyrics were scrutinized by the press, suggesting the song is about her relationship with ex-boyfriend, Justin Timberlake: 'I may have made it rain / Please forgive me / My weakness caused you pain / And this song is my sorry.' Our No. 4 Britney Spears song reached No. 15 on the U.S. Hot 100 and No. 1 in Australia and the UK.

3) 'Gimme More'

Despite receiving mixed reviews -- mostly about the opening line -- the electro, funk-sounding hit reached No. 3 on the U.S. Billboard Hot 100, becoming Spears' fourth highest-peaking single in the U.S. Her only public performance of the song was at the 2007 MTV Video Music Awards which received poor reviews, mostly for her lip-synching and forgetting most of the choreography.

2) '3'

Spears newest single -- produced by Swedish songwriter and producer Max Martin (who also collaborated with Spears on 'Oops!...I Did It Again,' 'If U Seek Amy' and 'Stronger') -- is even more electropop than 'Gimme More,' featuring a prominent bassline and heavier synthesized vocals. Oh, and did I mention it's about threesomes?

1) 'Oops!...I Did It Again'

Included on her same-titled album, our No. 1 Britney Spears rated song reached No. 9 on the U.S. Billboard Hot 100, peaked within the top five in all European countries, and produced her one of her most memorable music videos (who could forget the astronaut, racy-red catsuit, and 'Titantic' reference)? At the 2000 MTV Video Music Awards, Spears' controversial performance of this song -- which also included her cover of The Rolling Stone's '(I Can't Get No) Satisfaction' -- showed her stripping down to a flesh-colored stage outfit covered in Swarovski crystals.