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Miley Cyrus is wearing an oversize sweatshirt and nothing else, curled up in an enormous trailer parked outside Soundstage 24 at Paramount Studios in Los Angeles. She's just unpacked her "kit," which is what the 20-year-old pop star calls the gym bag full of over-the-top, blingy, fabulous accessories that she brings everywhere. There are Chanel logo suspenders and belts, Versace Medusa necklaces and brooches, spiked stilettos, hats, and miles of shiny gold chains. "I never know when I'm going to be like, 'Photo shoot!' And need some weird stuff to whip out." What if there's a sudden swarm of paparazzi? Or worse: "What if I get to a photo shoot and the stylist just sucks? So I bring my own shit." Cyrus, whose fourth album, Bangerz, is out this month, today is filming an MTV promotion—and, sure enough, when she's dressed in a tight white crop top and tiny black shorts, she dips into her kit to layer on gold necklaces and a low-slung vintage Chanel chain belt.

It's been a year since "I started trying to take over the world," she says, unknowingly paraphrasing a comment that Madonna made on American Bandstand nearly three decades ago, when she herself was an over-accessorized twentysomething. (In 1984, asked by Dick Clark what her future plans were, Madonna responded, "To rule the world.") It all began when the fresh-faced Disney star shaved the sides and back of her head, leaving a shock of platinum on top. "It changed everyone else's life more than it changed mine," Cyrus says with a laugh about her new 'do. But she's not kidding: Since wrapping the Hannah Montana series in 2011, the little girl who led a double life on a top-rated kids' TV show has reemerged in the public sphere as a provocative pop sensation.

The new look apparently had been brewing for some time. Cyrus released the album Can't Be Tamed during her final year as Hannah Montana. When the series wrapped, she semiretired. "I took off and I just wanted to party. I worked so hard, and I wanted to buy a house and just chill." She moved out of the house she shared with her parents, the Southern crooner Billy Ray (he of "Achy Breaky Heart" fame) and Tish Cyrus, and in with her fiancé, Liam Hemsworth. "I was an adult when I was supposed to be a kid. So now I'm an adult and I'm acting like a kid," she says. There are times when I'm sitting in my big ole house and I'm like, 'I can't believe I'm allowed to be here alone.' " (She and Hemsworth have been reportedly on and off and back on, but she declines to talk about their relationship. She will, however, say that she still plans on getting married. Eventually. "I definitely don't have time to deal with a wedding right now. But I will at some point.") She bought a car, a white Maserati with a Ferrari engine, and built a skate ramp in her backyard because she was too famous to go to the skate parks in her neighborhood. "I want my house to be the party house!" she says, flashing a big smile lined in bright-red lipstick.

On the point of partying, Cyrus brings up Justin Bieber, whose teenage rebellion is in full stride (as evidenced by the monkey incident and naked YouTube serenades). She wants to elaborate on the advice she recently gave him: "I'm not saying you need to take a break because you're crazy. I'm saying you need to take a break so you can be crazy, and people aren't going to judge you. You're going to do dumb stuff from here on out. But do it in your own time. Do it safely. You can afford to protect yourself and still have fun." She likens it to celebrities who get arrested for drunk driving. "Why don't they just get a driver?"

Blinged out, blindingly platinum, and with that banging body on display, it's clear that Cyrus is in the driver's seat of her new image. Take the much buzzed-about music video for her hit "We Can't Stop," which shows her cavorting erotically with life-size plushy toys. "We're in a world of selfies," she says of the unconventional glamour shots in the video. "I told my label: 'This is the first time I'm showing you what I'm bringing to the table as an artist. If this goes wrong, you never have to trust me again. I'll be your little puppet. But if I'm right, then you know I'm on to something.'" In fact, she was on to something—the video racked up almost 11 million views on its first day on Vevo.com.

Her ability to twerk, a slang term for hip-hop's brand of booty popping, debuted in the video too. Cyrus says she learned to twerk when she'd travel to Atlanta from her native Nashville and go to parking-lot dance-offs with girlfriends. They'd listen to music at tailgate parties and practice gyrating their bottom halves. "Not the country girls who are wearing the little frilled skirts and cowboy boots," she adds. Suffice it to say, she's not trying to tread on Taylor Swift's turf. What's Cyrus's country niche? "There is no girl out there speaking on behalf of the country girls who are turnt up."

While Cyrus is bristling with attitude, she's kept her feet on the ground paved by her famous father. "My parents always had money, and I've always been around this industry, so I didn't have my mind blown or become obsessed with being famous," she explains. Before moving, at the age of 13, with her entire family to L.A. to film Hannah Montana, she lived on a 500-acre farm where the children could do whatever they wanted. Her new California life wasn't that different. "When I was growing up, I didn't even notice that I started making all this money. There's something about new money that makes people change. But I never did not have [money]. So when I got it, I didn't become obsessed with having it."

She trusts her instincts, and runs with a discreet crowd. "The other day I saw that Lindsay Lohan was getting rid of, like, 80 of her friends because she wants to cut out the toxic people. I'm like, 'Honey, you're going to have to move out of this universe because everywhere you go there are toxic people.'?" Her best friend is her makeup artist, and most of her friends aren't famous—and are boys. She likes when they ask to drive her Maserati, and she lets them.

Her makeover mentor and album coproducer is Pharrell Williams, who had two hits of his own this summer. (You'd have to be living under a rock to have missed his "Blurred Lines" with Robin Thicke and "Get Lucky" with Daft Punk.) "His philosophy is that it's not what you're wearing, it's the way you wear it. It's not about the music you're making, it's how you're making it." She says he encouraged her styling in the "We Can't Stop" video too. "I feel like every girl is trying to have a beauty shot and prove that they're 'fashion.' But I can be in white leggings and a white sports bra and I'm on a whole other level of shit that those girls don't even get yet because they don't know how to do it." Cyrus calls Williams her "rock," the one man she can trust with her music.

He is equally effusive about Cyrus, who left a lasting impression on their first meeting. "I remember saying she was different," Williams recalls. "She was very clear as to what she likes. I kept thinking, 'She's got something.'?" What was it like to work together on the new album? "She has a crazy range like you wouldn't believe. And I really like that she is expressing herself." He's not worried about her falling off the deep end either, like so many other child stars. "It has a lot to do with her parents and the way she was raised," says Williams. "There's a thing Southern people understand that's hard to put into words." Maybe it's just that: Even though Miley's a second-generation performer, the Cyruses still aren't showbiz people.

To that end, she's put acting on the back burner for now. "I don't really care to do anything acting-wise," she says. "I want to make all of my music videos so epic that it feels like I'm still involved with acting." Hannah Montana may have burned her out. "I had to have [the producers] put sun lamps inside because I was getting depressed from a lack of vitamin D," she says of the show's last two seasons, after the franchise expanded into films and world concert tours.

Miley has dabbled in fashion too, but she wasn't completely fulfilled. She inked a deal with Walmart in 2009, then became disillusioned when the line didn't turn out as she'd hoped. "I went in there and saw, like, a puppy on a T-shirt. I was like, 'This is not what I wanted.' I wanted skinny jeans, I wanted to bless Walmart with jeggings!" (Walmart discontinued the line in 2012.) She says she loves jewelry and would consider doing that, when she has time: "Making real stuff with high quality. Not quantity. But not until I know I can give it 120 percent. I don't want to just slap my name on something."

All that's left is Miley and her music. Which turns out to be the one thing in her life that's not stressing her out. (In addition to her own reportedly rocky relationship, her parents separated and then reconciled this summer—another topic she'd rather not discuss.) "I'm someone who cares about the real things in life. There are things that are personal that stress me out, but my career? That doesn't affect me. I know I'm doing what I'm supposed to be doing." She lifts her fingers, which are tipped with long dagger nails and stacked in gold rings, and pushes her platinum bangs out of her face. "I'm not scared of anything."

CLICK HERE TO MILEY'S MUST-HAVES.

Pictured above: Unstoppable. Dress, Saint Laurent by Hedi Slimane, $5,990, 212-980-2970. Earrings, Chopard, 800-CHOPARD.