Gender is a hot topic in the broader culture and retailers are tapping into the phenomenon with their own definitions of gender, through unisex, gender-neutral and androgynous lines.

This month Guess announced a line called His & Hers, a collection that it says balances both masculinity and femininity. Available for sale in October, the range essentially strips color and most silhouettes out of the designs. In an interview with Complex, Guess CEO Victor Herrero said that the company was inspired by “cultural shifts that create movements such as this unisex phenomenon.”

Zara unveiled a unisex, or “gender-neutral” line earlier this year, while high fashion brands including Marc Jacobs and Hermes have blurred the line between collections. Also this month, Alexander Wang teamed with Adidas for an 84-piece unisex line that is somewhere between athleisure and high fashion.

Adidas x Alexander Wang

Adidas x Alexander Wang

As with gender itself, retailer approaches fall along a spectrum. There are lines that both sexes can wear, menswear for women, and anything in between.

There have been smaller brands with genderless, gender-neutral or unisex identities for years: TillyandWilliam, 69 Denim and Gender Flux have for their entire histories, almost, featured clothing both genders can wear. But high street brands like Guess and Zara are only now starting to launch these collections.

In the last three years, Lyst, for example, said it’s seen the lines between gender categories blurring. Editorial director Katherine Ormerod said that there has been a 108 percent increase in sales of unisex products in the last year. “We’re also finding customers search across genders, for everything from cult brands such as Acne and Public School to Asos and Zara. Whether or not we’re on the track to post-gendered shopping, it’s clear that an androgynous aesthetic is going nowhere.” Genderless searches make up now 23 percent of the site’s traffic, an increase of 9 percent from last year.

A lot comes down to shoppers under 30, a group that is much more comfortable with gender fluidity than its predecessors. Bloggers like Danielle Cooper of She’s a Gent and Sara Geffrard of A Dapper Chick have brought men’s styles for women into the mainstream (they’re both millennials.) And celebrities like Jaden Smith are comfortable wearing a skirt while women walk in “men’s” fashion shows. According to a 2016 report by JWT Intelligence, 44 percent of Gen Z buy things aimed at their gender. “This generation is more tolerant and are now growing up to be influencers,” said WGSN retail editor Sidney Morgan-Petro.

The trend extends to jewelry, too. Gamin has created unisex lines for Spring 2017. Even in naming, “post-gender” or “unisex” names are on the rise. Baby naming site Nameberry last year said names given to both boys and girls are one of the biggest trends for 2016.

Zara's unisex collection

Zara’s unisex collection

But while the post-gender trend is unmistakably relevant to a lot of people, retailers run the risk of appearing opportunistic or pandering if they play the card to ham-fistedly: “As a brand you don’t want to tap into transgendered models for your campaign or have gender neutral clothing, and then all of a sudden a year later you don’t,” said Morgan-Petro. “That reads as not being authentic.” Guess, for its part, hasn’t said yet whether it would do a second His & Hers collection.

For Morgan-Petro, “gender neutral” as a term itself is essentially used for marketing. With knitwear and easy silhouettes and the rise of athleisure, everyone can wear similar, if not the same clothing. Which poses its own challenges: When Zara launched “Genderless” in March, it was slammed for assuming that genderless meant gray, boring or shapeless. It’s slowly changed the collection, adding more color and shape. For many transgender people, gender neutral doesn’t boring, it meant a redefinition of who exactly can wear a skirt in the first place.

And retailers need to figure out what to do with it. Many of them break these desgns out into “gender-neutral” or “unisex” categories. “That’s what creates the buzz,” said Morgan-Petro. And yet, people who want to be gender-neutral want gender to be just that: neutral, not a third or fourth category or shunted off to the side.

For example, last year, way ahead of unisex catching on in the U.S., U.K. store Selfridges opened a pop-up retail experience called “Agender,” featuring sexless mannequins in clothes by Gareth Pugh and Haider Ackermann. It was a bold move, but mostly a marketing experiment. As fashion writer Katherine Whitehorn pointed out in the Guardian, ordinary pants, shirts or sweaters are all genderless already.

Along with the cultural impetus, however, gender-neutral and unisex clothing fits neatly within the zeitgeist of what is in style right now anyway. According to Edited, among the biggest runway trends for Spring 2017 were skate silhouettes — an nod to the fascination with 90s culture that has extended into more unisex and gender-neutral clothing, including hoodies and loose tops. Streetwear and athleisure both include styles that both men and women already wear. These “sit well with the street style stars and off-duty model looks, but retailers will have to think carefully about how to translate the androgyny for their own customer,” the trend forecaster said.