On 2001's Britney, Britney Spears sang about the struggles of growing up -- she wasn't a girl, not yet a woman. But by 2003's In the Zone, she had clearly arrived as the latter.

That album -- released 15 years ago on Nov. 12 -- marked the singer coming into her own, both as an artist (Spears took on more writing responsibilities than ever before) and as a woman (the LP's erotic content made "I'm a Slave 4 U" look relatively chaste). From the ice-blue album cover to its chilling production, In The Zone signaled a more mature direction for Spears as she explored electronic music and hip-hop like never before. And the record's lyrics -- which referenced her breakup with Justin Timberlake and pushed back at her critics in the media -- celebrated new levels of independence and candor for the singer.

Spears' hands-on artistry was rewarded by the public: In the Zone debuted atop the Billboard 200, went double-platinum and introduced some of the most iconic singles of her career. To celebrate the album and the turning point it provided for Spears' career, Billboard ranked every song on the album's standard edition.

12. “Shadow”

The first of the two slow tunes on the album, “Shadow” is Spears’s version of an ‘80s power ballad. But even her tender, emotive vocals aren't enough to get out of the, well, shadow of “Everytime.”

11. “Brave New Girl”

“Brave New Girl” might as well have been a mission statement for the In the Zone era: Here, Spears sings about letting go of all the constraints that have held her back and vows do things on her own terms. Still, the overuse of Auto-Tune and vocal effects makes “Brave New Girl” more cheesy than captivating.

10. “Outrageous”

Let’s face it: “Outrageous” is a cursed track. From the controversial team-up with R. Kelly to the music video shoot where Spears injured her knee (which led to a cancelation of The Onyx Hotel Tour), the song is essentially the moment the singer’s career changed. But there is a silver lining: “B-girl ain’t lost the beat/ Jumped over drama and I landed on my feet” is as good a mantra for Spears' career as any.

9. “Showdown”

Swedish production duo Bloodshy & Avant are the masters behind this unsubtle bedroom anthem, which finds Spears instructing her lover to undo her zipper and likening their adults-only fun to an arena sporting event. But when it comes to overall sexiness, “Showdown” doesn’t, erm, rise, to the occasion of the album's more seductive tracks.

8. “The Hook Up”

Spears has experimented with reggae and dancehall in the past (see: ...Baby One More Time’s reggae-funk “Soda Pop”), but on “The Hook Up,” she sounds like she stumbled into the sweaty basement where Sean Paul shot his "Get Busy" video. The dance-instruction lyrics and hard-hitting bass make for a flirty vibe, though the occasional, slight patois in her vocal delivery didn't age well.

7. “(I Got That) Boom Boom” feat. Ying Yang Twins

“SHAWTYYY! WE FINNA GO TO THE CLUB AND GET CRUNK WITH BRITNEY...HAANNN!” still remains one of the best song introductions of the new millennium. “Boom Boom” saw Spears embrace her really cool and urban side as she drew from her Southern roots. Then throw in a naughty verse from Atlanta’s Ying Yang Twins, and you have a weirdly perfect ass-shaking theme song for the clubs -- and one of the most unpredictable pop-rap collaborations of the era.

6. “Me Against The Music” feat. Madonna

Compared to other lead singles from her previous albums, “Me Against The Music” isn’t as iconic. But it offers a solid taste of Spears' newfound experimental side -- from the funky guitar riffs to her rapid-fire singing, it's Weirdney through and through. And, of course, the inclusion of Madonna served as the ultimate “passing the pop torch” moment that many fans were waiting for.

5. “Toxic”

One of Spears' signature singles, “Toxic” arrives in the middle of In The Zone like a lightning bolt straight from outer space thanks to those near-ear-splitting Bollywood strings (courtesy of Bloodshy & Avant) that could easily soundtrack a horror movie. While other tracks on the album are meant to soundtrack what happens after the club, “Toxic” leads you straight to the dance floor with its frenetic bassline and glitchy breakdown. And the world was eager to get down with her: The single earned Spears her first and only Grammy win for Best Dance Recording and peaked at No. 9 on the Billboard Hot 100.

4. “Early Mornin’”

Who knew Moby could be so risqué? He co-wrote and co-produced this after-hours jam, in which Spears details some presumed one-night stands with a dude with "dark hair" and another guy named Joe. And it's a stand-out on In the Zone thanks to Spears' commitment to capturing the vibe -- the singer literally yawns, whispers and giggles throughout the track as she recounts her nights out, making it feel like an authentic snapshot of her life at the time.

3. “Everytime”

While Timberlake went the scorched-earth route on 2002’s post-breakup single “Cry Me A River,” Spears' purported response, “Everytime,” opted for something more nuanced and tender -- and totally heartbreaking. Her vocals are so soft and fragile, it sounds as if she just finished wiping away tears before getting in the recording booth. And the song’s lyrical message becomes even more haunting when you watch the David LaChapelle-directed video for the track, which appears to depict Spears' death and reincarnation following a paparazzi-induced head injury.

2. “Touch of My Hand”

“Touch of My Hand” was the first song Spears recorded for In The Zone, and it clearly shaped the album’s unbridled sensuality. Here, she takes part in a tradition of unapologetic, taboo-busting self-love anthems -- “I love myself, it's not a sin/ I can't control what's happening," she purrs just before the chorus -- and it deserves to be as much of a classic in that category as the Divinyls’ “I Touch Myself.” It's also a song Spears clearly loves: Despite being a deep cut album track, she's regularly included it many of her tour and residency setlists.

1. “Breathe on Me”

Taking a few notes from Madonna’s passion-filled Bedtime Stories, Spears delivers one of the most provocative songs in her catalog with the trip-hop inspired "Breathe on Me." Set to a woozy, tingling beat, the track finds Spears toying with the listener via come-hither whispers and references to climaxes -- a less-explicit approach than "Showdown," sure, but one that's somehow even more intense. (She drove the point home during the Onyx Hotel Tour, during which she writhed around a bed with a male dancer to this track.) It takes a superstar of Spears' caliber to make an ad for monogamy sound this freaky.