It’s been a while since we’ve seen the chart-dominating, conversation-commanding Christina Aguilera we used to know. Years, in fact -- until this March, when a stripped-down PAPER Magazine photoshoot reintroduced her to the pop world. Then last week, on a delightful Carpool Karaoke appearance, Xtina nailed her “Dirrty” vocal runs like it was 2002 again.

Then came teasers and the unveiling of Liberation, her first album in six years. The first single, “Accelerate” -- featuring Ty Dolla $ign and 2 Chainz, produced by Kanye West -- feels like a more sensual, mature take on Stripped. The excitement for Liberation, due June 15th, is palpable.

One word sums up Aguilera’s decades-spanning career: agency. She spoke her mind more freely than her fellow teen pop stars. As a young woman, her vocal ability and artistic ambition wowed us -- until those strengths turned into self-indulgence, catalyzing her slide from pop’s mainstream. Along the way, she released two polarizing albums, 2010’s Bionic and 2012’s Lotus -- and delivered a controversial (and much-memed) rendition of the national anthem at the 2011 Super Bowl.

When did Christina Aguilera’s voice become bigger than her singles? Has she become so defined by her vocal runs that we’ve forgotten her sheer personality? One of the biggest stars of the 2000s has, perhaps, become underrated. How did Christina Aguilera get here?

In 1999, vocal theatrics weren’t anyone’s top priority -- at least, not in the teen-pop realm, where singers had to be relatable. Away from the melodrama of Céline Dion, late-’90s teen pop blended American R&B and European dance-pop; the Backstreet Boys and their ilk worshipped Boyz II Men, but worked with Swedish producers like Max Martin and Denniz PoP. Britney Spears’ early TRL classics -- “…Baby One More Time," “Sometimes” -- voiced the romantic uncertainty in teenage girls’ heads.

But Christina Aguilera was unusually self-possessed, even at just 18 years old. Like Britney, she’d gone from The All-New Mickey Mouse Club to a major label. But "Genie in a Bottle," her debut pop single, wasn’t about trying to please a boy. “Hormones racing at the speed of light/ But that don’t mean it’s gotta be tonight” -- “Genie” put Christina in control. It topped the Billboard Hot 100 for five weeks, not exactly a modest beginning. But “What a Girl Wants," her follow-up, preached a surprisingly mature, humble message about love: “You waited so patiently/ While I got it together/ While I figured it out.”

Aguilera’s self-titled 1999 album hasn’t aged well. It’s under-produced and directionless, the product of A&R who lacked the songs to match her talent. But Christina’s a committed narrator, rendering believable lyrics as clichéd as “I turn to you/ For the strength to be strong.” She stood out among the pack: TIME Magazine called her "one of the most strikingly gifted singers to come along since Mariah Carey.” Christina couldn’t wait to grow up, though -- as she told Rolling Stone in 1999: “I always want to shock people, throughout my career. Like Madonna.”

In 2001, “Lady Marmalade” raised a few eyebrows -- but performing alongside Pink, Mya and Lil’ Kim, as commissioned for the Moulin Rouge! soundtrack, and with Labelle’s original, explicit come-on sung in French, the culture didn't read too much into Aguilera's involvement. With 2002’s Stripped, however, Christina became “Xtina”: swapping blonde for brunette, her pale complexion for a tan, girlish outfits for assless chaps. “Dirrty,” the set’s advance single, borrowed its edge from hip-hop, via Redman and producer Rockwilder. The song was about sex, but the message was freedom. The key lyric: “It’s about time for my arrival.”

“Beautiful,” the second single from Stripped, remains the most important song in Aguilera’s narrative. Written by Linda Perry, former frontwoman of 4 Non Blondes, “Beautiful” voiced Christina’s darkest life experiences: growing up with an abusive father, struggling under the spotlight, and ultimately, refusing to be defined by how anyone else saw her. At Perry’s insistence, the final version of “Beautiful” kept Aguilera’s vocal demo -- recorded in one take, imperfections left bare. The iconic video depicted a diverse range of people struggling with discrimination, self-image, and gender and sexual identity -- it was daring for 2002, and no less potent today.

Stripped showcased an artistic leap as big as Aguilera’s change in image, incorporating R&B, Latin pop, classic and neo-soul. The sequencing doesn’t quite work, and at 77 minutes, it’s too long -- but Stripped’s messiness feels authentic. Aguilera defied society’s expectations of young women (“Sorry I’m not a virgin/ Sorry I’m not a slut”) and instead pushed her voice and persona to their limits, forcing you to accept and reconcile every side of her. Songs as wildly different as “Fighter," “The Voice Within” and “Can’t Hold Us Down” didn’t contradict each other. Taken together, they form a message: Be whoever you want to be, and be true to yourself.

If Stripped seemed mockable then, it seems nothing but brave now. Critics were still more invested in indie guitar rock than pop, while the gender divide of the TRL era made her Aguilera a cultural punchline -- to Fred Durst, Eminem, and SNL. Following in Madonna’s footsteps, Aguilera took up the mantle for sex-positive feminism, and opened herself up to ridicule in the process. Stripped continues to resonate long beyond its cultural moment; it’s been cited as an influence by the likes of Miley Cyrus, Selena Gomez and Demi Lovato.

But Aguilera recognized that she couldn’t push the boundaries any further -- how could she get dirtier than “Dirrty,” angrier than “Fighter”? So in 2006, at just 25, she went Back to Basics, making her most ambitious record, a double album inspired by the jazz and soul music of her childhood, and the hip-hop of the present. She worked with the likes of DJ Premier, Mark Ronson, Linda Perry, Rich Harrison, shouting out her musical influences in her lyrics: Marvin Gaye, Etta James, Billie Holiday, John Coltrane. With her pinup look, and now-trademark red lipstick, Aguilera wanted to be modern and eternal.

Back to Basics is Aguilera’s most comfortable, most musical album -- she’s completely within her element. But it’s also her most exhausting -- she brings her vocal acrobatics on nearly every song. Her vocal runs came to define her; those brash “heeeeyyyyy”s in “Ain’t No Other Man” and “Candyman.” She was always impressive, but across 19 tracks? And her recordings were relatively restrained compared to her live shows, where she’d adopt an even more demanding vocal style, taking no shortcuts.

Each of Aguilera’s first three albums feels like an endpoint. She’d exhaust the full potential of one sound and image before moving onto the next. But 2008’s Keeps Gettin’ Better: A Decade of Hits pointed the way forward, collecting her singles along with four new, sleek electro-pop tracks. The futuristic title track, “Keeps Gettin’ Better,” was Christina’s last solo top 10 hit on the Billboard Hot 100 to date. But more compelling are “Genie 2.0” and “You Are What You Are (Beautiful),” reinventions of two of her biggest hits. They downplayed her vocals -- and she’d never sounded more sultry, more hypnotic. Those new songs seemed to pave the way for her highly anticipated fourth album.

In interviews before the release of 2010’s Bionic, Aguilera spoke of having nothing to prove. She seemed inspired, working with indie-electro artists of the moment: M.I.A., Le Tigre, Peaches, Ladytron, Santigold; and cutting-edge producers: Polow da Don, Tricky Stewart, Switch and John Hill. But the album’s Terminator-inspired cover was polarizing, and so was its first single. “Not Myself Tonight," an electro-pop club jam, felt like a forced reinvention -- Christina telling, not showing, her transformation into… what, exactly?

It should have been the most forward-thinking pop album of 2010. But Aguilera was never truly able to become “bionic”-- the title track opens by glitching her voice, but for the most part, the album’s electronics happen around her. The results felt like she had put on one costume too many, and lost the emotional center of her music in the process. Some collaborators couldn’t translate their appeal into chart pop: M.I.A.’s wonky “Elastic Love,” Le Tigre’s “My Girls,” the promising Ladytron and Santigold contributions that were relegated to bonus tracks. Aguilera caught other collaborators too early, before they were household names: Nicki Minaj’s raunchy “Woohoo” verse is a highlight, but Sia’s stripped-down piano ballads are a touch too lethargic, unlike the melodramatic singles on which she’d later build her brand.

As a piece of music, Bionic is always listenable, if underwhelming. But in the pop sphere, it was a victim of its own hype. We wanted Xtina to reinvent pop music, but she couldn’t successfully reinvent herself. Bionic didn’t connect with radio, and sold significantly less than Back to Basics. When Aguilera soon indefinitely postponed a 20-date tour, it felt like the first time she’d ever admitted defeat.

From 2008 to 2010, pop had undergone a gravitational shift. Electropop, EDM, and a new generation of stars were ascendant: Lady Gaga, Katy Perry, Rihanna, Kesha, Miley Cyrus. Many saw Bionic as an attempt to rip Gaga off -- and the two’s on-again, off-again feud didn’t help. The truth is, they were both products of the same cultural shift -- Bionic would likely have happened with or without Gaga’s cultural imprint. But the younger, hungrier popstars had more to prove.

The 2010 film Burlesque was supposed to bring Aguilera’s star power to the silver screen. But its release, five months after Bionic, felt like a concession. Co-starring Cher, Burlesque cast Aguilera as a starry-eyed ingenue turned burlesque performer, in a story intended to parallel her real-life music career. But the notion of Xtina playing an everygirl seemed comical -- we already knew her as a diva! Burlesque didn’t connect at the box office, nor with critics, who seemed to miss the fact that it was intentionally, delightfully silly. The film had one lasting effect: Cher’s influence seemed to rub off on Aguilera, making her even more of a camp icon.

From 2011 to 2016, Aguilera was a judge on six seasons of The Voice -- a move that wisely kept her in the spotlight. The Voice has produced few long-term stars, but it spawned Aguilera’s single with fellow judge Adam Levine, Maroon 5’s “Moves Like Jagger” -- an enormous, Hot 100-topping hit that nonetheless felt like a conservative choice for Aguilera. In today’s Billboard cover story, she expresses regrets about her time on The Voice, describing it as a “churning hamster wheel.” Says Aguilera, “I didn't get into this business to be a television show host and to be given all these [rules] ... I would find myself on that show desperately trying to express myself through clothing or makeup or hair. It was my only kind of outlet.”

Still, following her success with The Voice and “Jagger,” the time seemed right for a comeback. But her 2012 album Lotus inspired more apathy than excitement. The lead single, “Your Body,” was her first collaboration with Max Martin -- the producer who gave her peers in Britney, *NSYNC and the Backstreet Boys their defining hits. “Your Body” should have felt like a momentous occasion, but it stalled at No. 34 on the Billboard Hot 100. On the album, Christina sings of rebirths and comebacks -- but despite its eccentricities, Lotus largely played it safe, fading almost immediately from our cultural memory.

Ever since, Aguilera’s musical output has been scattered. She dueted with A Great Big World on their surprise Hot 100 top 5 hit “Say Something,” a gorgeous piano ballad where her restrained vocals were barely recognizable. She featured on singles with Pitbull, Lady Gaga, Nile Rodgers -- often finding chart success, but each time aiming for pop’s middle, rather than commanding the center like she used to. And though her physical appearance has changed throughout the 2010s, her presentation’s stayed the same: red lips, big hair and makeup. “Xtina” felt less like a living thing, than an impossibly high ideal Aguilera had set for herself.

But Christina Aguilera’s always been in the back of our minds. Pop music moves so quickly that you don’t always process it in real time, especially if you grew up on it. Many of her fans were just kids during the TRL era, some of whom have grown up to be today’s pop stars. Xtina’s been cited as an inspiration by the likes of Camila Cabello, Sam Smith, Alessia Cara, Jessie J, Meghan Trainor, and Demi Lovato -- who’s set to duet with her on Liberation. We’re only now realizing how the icons of our youth influenced our outlook on music, feminism, sexuality. In 2016, Kylie Jenner dressed up as “Dirrty”-era Xtina for Halloween, kicking off a new wave of appreciation for Aguilera. If “Dirrty” was a costume Kylie could put on, perhaps Christina had simply taken it off.

Nostalgia is a powerful force, and right now, songs like “Dirrty” and “Beautiful” feel more relevant than Christina’s musical output this decade. But though Xtina’s influenced many, her brassy, melismatic vocal style is out of fashion. Today’s big-voiced popstars -- Miley, Dua, Ariana -- wield their ranges with more restraint. No one sounds like Xtina, which, in some ways, makes her ripe for a comeback. Could she, a household-name celebrity, be an underdog once again?

We didn’t know just how much we’d missed the old Christina Aguilera until we saw her re-emerge in PAPER’s Transformation Issue. The social media reactions were breathless. In 1999, Christina seemed mature beyond her years. In 2018, we’re stunned by how youthful she seems at 37. If she can turn back the clock on her looks, what about her music? It feels like anything’s possible.

Every failure is a setup for another comeback. For years, Christina’s seemed larger-than-life; she’s the big-voiced diva of her generation. But you have to humble yourself to be relatable. Even in pop, you can’t manufacture a blockbuster. You can only earn it organically, otherwise -- like the underwhelming responses to Bionic and Lotus proved -- it’s just empty hype.

Christina recorded her true debut single when she was 17. On “Reflection,” the theme from Disney’s Mulan, she sounds unbelievably precocious. Her voice is strong, but it wavers, seemingly out of nervousness, like it never would again -- live or on record. Christina couldn’t wait to become the diva of her dreams. But from “Reflection” to “Beautiful” to “Hurt,” the message of great pop stays the same: There’s no self-empowerment without vulnerability.

Two decades later, Mulan is old enough that it’s getting a remake. Christina Aguilera can’t turn back the clock, but perhaps she can come full circle. As she sang in 1998, “When will my reflection show who I am inside?” Liberation needs to tell us two things: who is Christina Aguilera, and what does she mean to the world in 2018? Only she can redefine herself. But the album’s title shows promise -- it suggests that she’s no longer singing for herself alone.