Indigo girl

When Michelle Siwy was 13, she took her birthday money and bought a Bonanza bus ticket to Boston. She told her parents she was off to a friend's house for the day.

Truth was, the Rhode Island teen was heading to Harvard Square to go shopping and comb vintage shops for old denim. Siwy had a habit of modifying her jeans to fit her adolescent taste and sensibility.

"When I couldn't get into Boston, I'd go to the Salvation Army every Thursday, when they'd put new stuff out, and scour the racks until I'd find the perfect jeans," Siwy recalls. "I'd take them home, add patches and flowers, as girls do, and then rip them and wear my tattoo tights from Urban Outfitters under them."

Siwy no longer has to customize old jeans. The 31-year-old now has her own denim collection, called Siwy. The line has been so successful that half of Hollywood -- not to mention fashionable New York types -- seems to be slipping into Siwy denim. Kate Moss, Nicole Richie, Sienna Miller, Lindsay Lohan, Naomi Campbell, Beyoncé -- they've all been spotted sporting her jeans and shorts, known for the quilted "Siwy heart" pockets on the back.

Not bad for someone who just launched her line in 2005 .

Siwy began designing long before that, long before her first illicit trip to Boston. When she was a child, growing up in Central Falls, Siwy was in a serious car accident that left one of her legs disfigured. It took several complicated surgeries to correct the damage, which meant many months stuck in bed.

To pass the time, Siwy devoured fashion magazines and began to sketch her ideas. Eventually she began altering her vintage jeans, sometimes bleaching them in the washing machine or putting them in the dryer with different materials to manipulate the finish of the denim. Years later, she was still doing it, even while enrolled in nursing school. After taking a summer class at New York's Fashion Institute of Technology, Siwy knew what she needed to do. She transferred to the Rhode Island School of Design , where she learned to master the sturdy cotton twill that so obsessed her.

Out of school, Siwy worked for several clothing companies, always ending up in charge of the denim department. She was happy designing, but she was always doing it for someone else, which left her frustrated. Siwy knew what kind of jeans she wanted to wear, what her friends wanted to wear, what women wanted to wear, but she couldn't make them. One day, she opened up to her boss, the owner of the children's clothing company, and suddenly had herself a financial backer.

What initially set Siwy apart from other denim lines was her embrace of skinny -- or narrow- leg -- jeans at a time when stores were still awash in boot-cut styles. It was only one of several design elements that have made her jeans so popular.

"I was always having my jeans tailored to be more narrow all the way down the leg," Siwy say s . "A lot of retailers didn't get the skinny jeans at first, so they only ordered the boot-cut style from me. Then, a few months later, when their orders were coming in, everyone was suddenly asking for skinny jeans, and all the buyers changed their minds and ended up exchanging their boot-cuts for the skinnies."

Half Polish and half Vietnamese, with long, dark hair and a willowy figure, Siwy could be a model for her own line. But the designer has devised a cut that flatters women of many sizes. While her jeans manage to make fans look as lean as Kate Moss from the front, turn around and it's all Beyoncé curves. Thanks to the perfect placement of the trademark "Siwy heart" pockets, women look a little more rounded from behind.

"I constantly find myself staring at people's butts all the time," Siwy says, laughing. She's seated in a cafe in her new neighborhood, Manhattan's trendy Lower East Side. Aside from her booty fixation, Siwy designs every other aspect of her jeans for the female body . The seams and waistbands are shaped and contoured to hug curves and the "vintage" washes are faded in just the right places, contouring the legs like the defined muscles of a Sports Illustrated model. Siwy's fall line will retail for about $150 to $230.

Bobbie Thomas , style editor for NBC's "Today Show" and co-host of "Fashion Police" on the Style network, can't get enough of Siwy jeans. Not only does she wear them, but she recommends them to her viewers.

"I loved that for the first time, someone really embraced curves," Thomas says. "It's for a woman's body and it really features a feminine silhouette and celebrates that. It was not a shock to me that she was embraced by Hollywood. Actresses are people too."

Elisa Goodkind, a New York stylist who's worked with Catherine Zeta-Jones and Vanessa Carlton, says she too is "obsessed" with Siwy jeans.

"I wear them almost every day," she says. "Everything comparative feels like mommy jeans."

Siwy's bestsellers are her ultra-lean, ankle-cut "Hannah" style, followed by her cut-off shorts. "It's hard to find a pair of shorts that look like you just cut them yourself," she says.

Although the age of the skinny jean doesn't look like it will end any time soon, Siwy is working on what she imagines will be the next wave of denim: high-waisted skinnies and wide-leg denims. Next year, she'll also be including some T-shirts in her collection.

"I can sit on my fire escape for hours just people watching ," she says. " I'm on the direct pulse of all the experimental fashion that's going on -- I get to see what's out there before anyone else does. That gives me an edge I can incorporate into my collection."