In January, Gucci's menswear runway collection was an eye- opener.

It was not because the brand had just fired its nearly decade- long creative director Frida Giannini in December or that new designer Alessandro Michele had pulled the collection together in less than a week in his new role.

It was because the men on the runway looked... like women.

In fact, some of them were women - an increasing trend in menswear shows. Models of both genders - waifish male models and boyish female models alike - were wearing silhouettes, fabrications and items of clothing that traditionally appear in womenswear collections.

Michele's deliberately ambiguous outfits featured massive pussycat bow blouses, shrunken jackets and low-slung, wide-leg trousers on willowy models with matching soft features and lengthy, undone hair.

And just like that, this change in creative direction became symbolic of an industry-wide trend - and Michele the movement's unofficial leader.

A shift towards androgyny has been building over the past two years and with Gucci's new experimental take, it has hit its stride. (It is worth noting that the recently slumping Gucci just reported its first sales growth in two years, a 4.6 per cent increase for the second quarter of this year - up from a 7.9 per cent decrease in the first quarter.)

Gender-bending is nothing new in fashion or pop culture. But in large-scale, high-end fashion, the theme has not been conveyed as loudly or as frequently since, well, a young Mick Jagger, David Bowie and Marc Bolan toyed with feminised looks in the late 1960s.

But today, thanks to a troupe of contemporary designers - such as Rick Owens and J.W. Anderson - this theme of gender-neutral dress has been reimagined.

"The concept of androgyny comes up from time to time in fashion," says Ms Nancy Deihl, director of the costume studies master's programme at New York University. "In modern fashion history, two of the most notable examples are in the 1920s and in the late 1960s into the 1970s."

She notes that both were periods of social upheaval, which reflected an empowered youth culture. "The post-World War I generation and the baby boom that created the young population of the 1960s represent times when young people had a lot of economic and cultural influence."

Hello, millennials.

"Androgyny is not a passing trend, but one that is going through another cycle with a new generation," says Mr Tom Kalenderian, executive vice-president and general merchandise manager for men's at Barneys New York.

Like Ms Diehl, he points to music subcultures as a source of unisex movements past and present and also to a small cadre of before-their-time fashion designers.

Rudi Gernreich, who after the turn of the last century began dressing women in men's suiting, was one such oracle.

"Costume designers often appropriated Gernreich's vision when designing costumes for science-fiction flicks, often proposing men and women in futuristic outfits that were quite similar."

In the future, in other words, artists imagined that in the 2000s, clothes would just be clothes.

These days, this mantle is carried by successful, high-end designers such as Hedi Slimane at Saint Laurent and Riccardo Tisci at Givenchy, who favour traditional feminine elements such as capes, skirts and tights in their menswear runway collections. But does this translate to mainstream sales?

"Gender play on the runway doesn't just attract a customer who wants an androgynous look, but also a consumer who likes smart clothing with a forward- thinking story," says designer Charles Haribson, who is known for showing his womenswear collection on female and male models.

Department stores are now toying with devoting floor space to unisex clothing.

In January, Selfridges launched the Agender Project, a curated section of the store showcasing the retailer's gender-spanning lines, such as Nicopanda, Comme des Garcons and Gareth Pugh. The experimental floor closed its run in April.

And consumer habits about gender traditions are getting broken down at younger and younger ages - a new string of start-ups are attempting to obliterate the barriers between clothes that are designed for young boys versus those designed for young girls.

In pop culture, public tastes are dictated in large part by celebrities - movie stars, musicians and athletes have a large say in how younger generations shop and dress.

For every Bowie and Jagger in the 1970s, there is a Jared Leto or Kanye West wearing a skirt on stage in 2015.

The next two years will see this trend increase, according to Mr Kalenderian.

"Clients are receptive," he says. "Ultimately, it is more about beautiful clothes that are rare and special.

"It is more of a sidebar note that these clothes are stylistically less rigid than what we perceive to conform to a definition of masculine versus feminine."

BLOOMBERG