First of two articles

At a boutique in Potomac where denim dreams come true and almost no one is bigger than a size 10, a woman flags down a salesgirl and confides a terrible problem.

"You don't have a butt?" asks the salesgirl, Mandy.

"Like, at all," the woman says.

This is as close to an emergency as you can get in the premium-denim world. From the rows and rows of bluejeans, which stretch to the right and left, from floor to ceiling, Mandy pulls a pair of Rock & Republic's with high back pockets, designed to magically lift and shape all that is droopy or flat.

There are nearly 30 brands here at B Scene: jeans with small pockets and big pockets and specially angled pockets, jeans with close-together pockets that make a wide butt narrower, jeans with no yoke to make a butt extra round. There are rhinestoned and embroidered pockets to call attention to your butt, and plain pockets to make your butt disappear. Everyone has a different theory about how to solve the world's butt problems.

"There's so much controversy," says Ilana Kashdin, who once planned to be a doctor and now co-owns this boutique, where she studies the anatomy of denim and the derriere.

Whether you're paying $145 or $520 for premium denim, you want to get the butt right. It's the second thing every woman looks at in the mirror, but it's the first thing she cares about. She does that half-twirl, her back arched and her head craned around. If the jeans are right, the experience is transformative, like putting on a magic cloak.

She says, "Oh. Muh-god."

For a while we were stuck in a dark place, our jeans tragically utilitarian. We bought them in stores decorated with hay bales. We fooled with acid washes and elastic waists. We had poor pocket technology. We had no choice.

Then came beauty, so much beauty. (And status, too, but we'll try that on tomorrow.) Now we are clad in the sanctified denim of the 21st century, a pragmatic, pioneer material made decadently new. From our perfect behinds, we can see the future.

In the Cabin John Shopping Center next to a tanning salon, B Scene is the province of cute teenagers and hot moms. They come for sequined shrugs and $120 metallic sandals; velour sweatshirt-and-skirt ensembles ($275); tube tops made of terry cloth. ("Isn't this the material you make towels with?" asks a young man, and the young woman he's with calls him an idiot.)

And they come for the jeans, found in the back third of the store, where a ladder is propped so Ilana can reach the tippy-top shelves.

Premium denim is a tiny percentage of the overall jeans market, but you wouldn't know it from the profusion of brands here. A disproportionate number have names that sound less like fashion lines and more like spiritual causes that Hollywood actors might get involved in. There's True Religion and Blue Cult, Citizens of Humanity and 7 for All Mankind. This makes a certain sense; the notion of denim-as-transcendence will ring true to any woman who has ever looked in the mirror and not recognized her own blue-clad behind.

What if we all adored our backsides? Would we achieve harmony with our bodies? Could this translate to a higher level of consciousness? Are the jeans of the 21st century helping us get there, or making sure we never do?

"I live for jeans," says Becca Walker, 33, who has between 20 and 30 pairs and recently bought some made by a company called People for Peace. They cost $285 and have the word LOVE embroidered on the butt, along with a butterfly. These made Becca an object of envy. Women at her son's nursery school were "stalking" her. Her neighbor went and bought a pair. Walker thinks the jeans were totally worth the money. "I felt a little nauseous afterwards and then I was okay," she says.

At B Scene there are dark jeans for nights out and light jeans for days in. There are white jeans with pink stitching and blue ones with turquoise-colored stones. There are jeans with worn hems to mimic the look you'd get if you let them drag under your flip-flops. There are jeans with wire in the back pockets to give them a perpetually wrinkled look. There's a style called "ripper," with the bottoms and pockets all shredded, and a style with the apocalyptic description "destroyed." There are maternity jeans with a little pouch for the belly. Soon Ilana will be getting shipments of baby jeans, costing between $80 and $180, and some extra-fancy adult jeans for $695.

There are even jeans for something InStyle magazine describes as "posterior overflow."

"They fit a little bit higher to avoid some of the spillage that we all get," Ilana says.

("Higher," of course, is entirely relative. Ilana's 18-year-old salesgirl Mandy Jasnoff puts on a pair of jeans that fasten two inches under her bellybutton. She's astonished. "I've never put on a pair of pants that's so high," she says.)

Occasionally, the store gets a newcomer to the premium denim world. This can be exhilarating and scary for the customer, like going to a foreign country without knowing a word of the native tongue.

"Did you want, like, daytime, nighttime, go both ways?" Ilana asks, surrounded by piles and piles of indigo. "Beat up, not beat up? Does a particular wash catch your eye?"

"I think, whatever?" the woman says.

The newbies often don't know one of the cardinal rules: If they're stretch jeans, buy them small. They'll feel tight at first but then they'll expand "half a size," Ilana says. If a woman isn't willing to buy her jeans this way, Ilana informs her she may have to wash and dry the jeans before each wearing. This is arduous, though not as time-consuming and expensive as dry-cleaning, which some other jeans require.

They start young at Ilana's store. Martha Ein often shops with her teenage daughters, who are permitted to spend no more than $200 per pair, though "sometimes they twist my arm."

"I don't have that many," says her 16-year-old, Lili, considering her denim collection. "Probably like 15."

A young woman comes in with her grandfather. In one fell swoop, he buys her five pairs of jeans and assorted other items for $2,451.86.

The more jeans you buy, of course, the more you need. Abundance is in itself beauty. So you have certain jeans in a Brooklyn wash, but do you have them in the New York Dark wash? If you accidentally bought the same pair of premium jeans twice, as one young teen did, who could fault your enthusiasm?

Ilana herself wears jeans so often she claims her pale leather car seat has taken on a blue cast. She buys premium denim for her 2-year-old son. She grew up in Gaithersburg and studied biology in college, planning to be a doctor like her dad, but instead followed her mother into retail. Now, like an ornithologist, she can read jeans in an instant from the subtlest of markings. She can tell that Teri Hatcher on "Desperate Housewives" likes to wear Hudson jeans, and that a recent "American Idol" contestant was wearing a pair of True Religions because of distinct rips in the leg.

Ilana is 31 but lithe as a teen, perfect for the denim lines she carries. The jeans in her store don't come with a waist size bigger than 32, so if you're larger than a 10 or 12, you're out of luck. (Heftier women may suffer the indignity of being pointed to the store's small collection of men's jeans.)

B Scene is the destination for a 14-year-old who says, "Now I'm back to a 25," and a 24-year-old who boasts she's been the same size since 16. This is where you hear Ilana asking: "This is too big? This is the zero."

Still, premium denim customers seem to have problem bodies. They're too tall or they "fit into jeans weird." Some say that's why they have to buy expensive jeans.

"My problem is I have thick thighs and a tiny waist," says Heather Vaughn, 35, who has the body of a Maxim cover girl. She's trying a pair of jeans that look spackled on. "I feel like a sausage link," she says, and performs some deep squats in front of the mirror. She turns to her friend. "You don't think I look fat?"

"No, you don't look fat," the friend says.

"The darker the jeans, the thinner the look," Heather says, like a fashion Confucius, on her own path toward denim enlightenment.

Tomorrow: Distressing moments.

B Scene co-owner Ilana Kashdin, left, helps shopper Claire Thibeau, 16, at the Potomac store. Top left, a pair of Paiges.People for Peace jeans with butterfly embroidery and rivets, above, can be yours for $285 at B Scene. Below, $275 Antik Denim jeans with turquoise applique and a $375 pair of True Religion jeans with patched pockets.Tara Loring, 17, pauses at B Scene in her quest for the perfect pair of pants.