Historically, modest clothing has often been at odds with what's considered "cool," especially in the classic American sense. This week, the Supreme Court heard oral arguments in the case of a young Muslim woman who was denied a job at an Abercrombie and Fitch store because her headscarf didn't fit in with the company's desired "look." As my colleague Emma Green noted, "'classic' Americans probably dress like Protestants—which is to say, they don't dress in much religious garb at all."

And yet as Abercrombie's profits continue to tumble, modest fashion's profile is rising, thanks in part to an increasingly outspoken number of trend-conscious religious Millennials who stand by the idea that covering up can be glamorous, sexy, and, yes, cool. Corresponding with the rise of Instagram and fashion blogs, these Christians, Jews, Muslims, and Hindus—mostly young women based in the U.S.—took to the Internet to vent their frustrations about limited fashion choices and to share creative tips for elevating their wardrobes. The result: growth and visibility for the modest-fashion movement and a new generation of religious-lifestyle bloggers, designers, and trendsetters from across the faith spectrum.

It’s a surprisingly enticing focus group for the fashion business. Millennials are much less likely to be “religious” than their parents, with 25 percent of the generation identifying as unaffiliated with a faith—nearly double the rate for Baby Boomers. But as the Pew Research Center’s study on "Religion Among Millennials" points out:

Millennials remain fairly traditional in their religious beliefs and practices … Though young adults pray less often than their elders do today, the number of young adults who say they pray every day rivals the portion of young people who said the same in prior decades. And though belief in God is lower among young adults than among older adults, Millennials say they believe in God with absolute certainty at rates similar to those seen among Gen Xers a decade ago.

Dressing conservatively according to a religious code can prove challenging. At the level of pure convenience, appropriate pieces need to be cherry-picked from across several stores. On a broader scale, professional dress codes are often unfriendly to, or at least limiting of, religious attire: Last year, for instance, the Pentagon made new concessions for members of the American military to wear turbans, head scarfs, and yarmulkes if they asked permission; advocacy groups fired back, noting the "presumptive bar" remained.

And for young people, there’s the ever-important issue of wanting to fit in and look trendy while maintaining their sense of uniqueness. Take fashion blogger Chandra Leonardo: An Apostolic Christian from northern California, Leonardo details her conservative outfits on her website MoMoMod (short for "More Modern Modesty"). Growing up, she says, she always felt out of place among her peers. She wore maxi skirts years before they regained mainstream popularity as the carefree weekend staples of boho-chic celebrities.

Among the best-known names associated with the modest-fashion movement is perhaps Summer Albarcha, otherwise known on Instagram as Hipster Hijabis. The 19-year-old Muslim started Instagramming her outfits in August 2012 and quickly built up a fan base (she now has more than 47,000 Instagram followers) that includes young Muslims, people of other faiths, and nonbelievers alike. “I really think [religious dressing] doesn’t have to look backwards or uniform,” said Albarcha, whose outfits range from leather pants paired with Chelsea boots and a plaid scarf, to maxi skirts and slouchy chartreuse sweaters.

One of Albarcha’s collaborators, Brooklyn-based shop Mimu Maxi, is another well-known, modest-fashion staple run by Orthodox Jewish sisters-in-law Mimi Hecht and Mushky Notik. The pair started their brand in the summer of 2013 with the Hasidic female community in mind, but Mimu Maxi soon gained a broader, loyal following. (This interfaith approach has hit rough patches at times: Last summer, the sisters saw a huge backlash for posting a photo on Instagram of Albarcha wearing a hijab.)

Of course, modest fashion isn’t universal in its rules or its politics. Muslim women adhering to the dress code are encouraged to cover their ankles and have sleeves up to their wrist, with only feet and face visible to the public. Hasidic women are required to cover the collar bone, elbows, and knees. While all the customs vary just a little—“Everyone has a different conception of what modesty is to them,” Albarcha noted—fabric choice, colors, and cuts offer a surprising number of unlimited options. In fact, bloggers across the religious spectrum continuously emphasize the freedom within being held to a dress code, often describing the challenge as “liberating” and “fun.”

That combination of freedom and restraint means there are huge avenues for business with modest fashion, particularly on a global scale. With a fast-growing Muslim youth demographic tuned into the latest fashions around the globe, a vast group of people is underserved by traditional fashion chains: There are nearly 800 million Muslims younger than 25, according to Shelina Janmohamed, vice president of Ogilvy Noor, an Islamic marketing agency.

“Not only do you have more Muslims to target, but they are increasing in numbers faster and they are young. And, contrary to a lot of expectations, they are interested in brands and they are interested in asserting some kind of individuality through what they purchase,” Janmohamed told Business of Fashion last year.

But the inclusiveness of the modest-fashion movement also means its appeal stretches beyond the faithful. Atheists are among the most vocally supportive on social media of modest blogs and Instagrams—a point everyone I spoke to made to me without prompting. “If you notice from our Instagram page, it’s not a small hobby,” Hecht said of Mimu Maxi’s social-media presence. “We’re not about being a fashion brand. It’s more about feeling good and being true to yourself, telling women to be authentic, genuine.”

This emphasis on authenticity in part explains another interesting variable in the modest-fashion trend: Part of its appeal to Millennials has hinged on its association with the nebulously defined “hipster” label. “[Hipsterism] is about being unique but not being too unique,” sociologist Kevin Lewis told me. “It’s marginal differentiation, where you want to be different enough from your peers but not so different that you want to be ostracized.”

Beyond Hipster Hijabi's name, there's the fact that Mimu Maxu is based in Brooklyn's Crown Heights—a neighborhood known as a rising hipster mecca as well as a home to a large Orthodox population. Consider the frequency with which “hipster” is appended to various religious identities (sometimes by members themselves): Mipsterz (Muslim hipsters), Jewish hipsters, and Mormon hipsters. The label "hipster," at the very least, is more inclusive and malleable than Abercrombie's preppy, "classic East Coast collegiate style of clothing."

Modest-fashion trendsetters like Mimu Maxi's Hecht and Notik don't shy away from the oft-scorned term the way their secular counterparts might. Before Refinery29 referred to the pair as "Hasidic Hipsters" in a video last year, the pair said they had never even considered the label. But, perhaps by dint of the cool factor or the broader sales appeal, they don't mind.

"People who shop with us who aren’t Jewish don’t really care about religion," Hecht said. "They just like the fabric and the cut. There’s Muslims who like us, atheist hipsters who like us. We’re not hiding who we are, and it’s cool.”