Between its tiny models, outrageous price tags and mind-boggling designs (hello, Hannibal Lecter masks), fashion isn't always the most inclusive of worlds. But recently the industry has been celebrating a shift to greater inclusivity when it comes to gender, with designers sending men and women down the runway in identical outfits and retailers ending the divide between men's and women's sections.

Unisex fashion — also referred to as ungendered, agender, genderless and gender neutral style — has created huge buzz over the past few seasons, with Gucci announcing plans to show its men's and women's apparel in one show, London department store Selfridges hosting a unisex fashion pop-up and high street giant Zara launching a line of ungendered basics.

Read more: A Very Important History of Men Wearing Crop Tops

And the change couldn't have come sooner for millennials. Half of us believe gender exists on a spectrum according to NPD Group, while a study by the Intelligence Group showed less than half like to buy gender-specific products.

But there's a catch. Up to now, the high street interpretation of fashion's agender movement has been restricted to "clothes that masculine folks usually wear," as one Twitter user described. Jaden Smith might be rocking skirts, but for the most part the clothing items currently shared by the sexes are traditional men's staples like sweaters, pants and jackets.

Hood By Air, Rick Owens and Givenchy Getty Images

Men, with the notable exceptions of Smith and Jared Leto, have yet to embrace the most feminine of items: the skirt. And it's not that designers haven't tried: Hood By Air, Rick Owens and Givenchy have all sent male models down the runway in skirts or dresses for recent shows.

But for mere mortal men in offices, bars and gyms, far removed from the hallowed halls of high fashion runways or the flower crowned bohemia of music festivals, unisex dressing has a limit. The lines might be blurred for shirts and jackets, but when it comes to skirts, the only line is a red one.

The lines might be blurred for shirts and jackets, but when it comes to skirts, the only line is a red one.

But it wasn't always this way. In the past, both men and women wore skirts, which are believed to be the oldest item of clothing after the loin cloth. Men in the Western world wrapped themselves in skirt-like garments from the times of ancient Rome until the French Revolution sounded the death knell for fussy, aristocratic dressing, leading men to ditch skirts.

And it's not like this is the first time fashion has tried to sell men on skirts in the modern era: Jean Paul Gaultier dressed male models in skirts in 1984 and Brad Pitt flexed his biceps in a mini dress on the cover of Rolling Stone in 1999. But neither persuaded men to re-adopt the skirt.

Rolling Stone

One-way androgyny: So why won't men wear skirts? After all, women have been wearing trousers for a century now, borrowing their boyfriends' Levi's and repurposing the tuxedo (thanks, Yves Saint Laurent).

"At this point in time in our culture, skirts are considered feminine, whereas pants are understood as more androgynous — hence there is a resistance to skirts amongst men, despite a surge in unisex fashion," Anna Akbari, sociologist and founder of Sociology of Style, said in an email. "Men in skirts is still largely perceived as cross-dressing, and it would take some major cultural shifts for that to change and for men in skirts to go mainstream."

Society's rejection of men in skirts is vocal and often cruel. Even Smith, who looks so good in a skirt he was chosen to model womenswear for Louis Vuitton, faced initial opposition to his gender-fluid fashion from famous dad Will Smith, who told him "you cannot wear a skirt."

Mic/Getty Images

And he wasn't the first to come under fire: Jared Leto earned the title of the World's Worst Dressed Man from GQ, with the magazine noting one reason for awarding him the title was the actor wearing "skirts about as frequently as pants." Kanye West was victim of some vicious anti-skirt lyrics after wearing one back in 2011, reportedly then demanding that Getty Images remove pictures of him in the offending garment from their archives.

"There seems to be a social stigma against men adopting a look that has any perceived hint of femininity, I think due to the wide net cast by deep-seated transphobia and homophobia, and an association of femininity with weakness," Joe Quarion, founder of unisex skirt startup Skirtcraft, which has a majority male clientele, said in an email. "With skirts or dresses literally symbolizing women on restroom signs everywhere, wearing a skirt or dress is considered a fundamental transgression."

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The skirt shift: The modern sartorial dominance of trousers means it is frowned upon for men in North America and Europe, with the exception of the kilt-wearing Scots, to leave the house in clothes without a built-in crotch, even though elsewhere in the world men are happy (and no less manly) wearing items like the djellaba or sarong.

And while there are some signs of a shift on and off the runway — not to mention online communities of skirt-wearing men like Skirt Cafe — it will take some serious work to fight society's deep-rooted resistance to men in skirts.

"Part of it is just that it will take time for the trend to build on itself," Quarion said. "I think it will accelerate, since people will adopt it more and more quickly as it becomes less rare. It will also depend on the decline of misogyny, homophobia, transphobia, as all of these hatreds and fears are wound up with each other and with views on things like skirts for men."

What it comes down to then is much more than a question of style. Men in skirts represent a victory for gender blurring, one that still looks like a distant hope as we struggle to consider more than hoodies, jeans and T-shirts in neutral colors as truly agender garments.