A staple wardrobe item for American women is getting a huge makeover

For years, the underwear industry has been primarily about sex. 

It's understandable, considering that the lingerie industry's behemoth Victoria Secret was founded by a man with the initial intention of welcoming them with open arms to a lingerie store.

Lingerie, traditionally, has been by men and for men, even if women are the ones wearing it.

But that's been changing.

Scores of underwear companies have emerged to appeal to the people who have to wear it: women. Negative Underwear has been focusing on functional, utilitarian, but high-quality underwear. ThirdLove has been zeroing on proper fit with a fancy app that uses photos to gauge proper bra size.

Then there's the latest crop of emerging underwear companies, and they're set on winning the hearts of women by designing menstruation-friendly underwear. 

Perhaps more so though than any other "female-friendly" underwear concept, these companies really, truly cater toward women. These ostensibly feminist companies ask women to celebrate components to womanhood that they've been previously told to be quiet about or struggle with.

The marketing campaigns have several pillars. For one, there's the initial shock. Secondly, it might not appeal to men - but that's the point. And thirdly, once the idea settles in, it makes sense. 

"For women with periods," some of Thinx's ad's declare - in other words, most women. 

Thinx has made waves in New York City with its ad campaigns in subway stations with grapefruits and leaking eggs and declarative, provocative statements.

This fall, it received an onslaught of press when Outfront Media - which controls subway ads -  tried to remove the ads, according to Mic. This was out of fear that children would feel the urge to ask their parents what, pray tell, are periods?

The ads went under review, but Thinx won the battle, The New York Times reported.

The "period" component to the underwear is that it contains a cloth that can absorb the blood. It's moisture wicking, leak resistant, and fends off bacteria. Founder Mikki Agrawal told The Cut reporter Noreen Malone that she could forgo using a tampon if she used Thinx. 

There's also Dear Kate, which calls its undergarments "performance" underwear. The company has been on a mission to disrupt the underwear industry since its inception. The company was founded by Julie Sygiel, a chemical engineer.

Dear Kate has been also been receiving adulation for its ad campaigns. Honing in on its 'tech' theme, the company has featured tech industry executives in its ads. The company has also outwardly knocked Victoria's Secret's "Perfect Body" campaign.

Dear Kate has also infiltrated the New York City subway system.

 There's also Panty Prop, which is slightly different, in that it's designed to hold a sanitary pad in place - but again, it's underwear designed to be functional for women and part of the larger for-women, by-women underweat movement.

"I literally started it because of having a problem," Crystal Etienne, founder of Panty Prop - which has a patented design - said to Business Insider. 

She believes that there was just an empty space in the market, and women are celebrating that they have options now.

"Even with the lingerie industry, like I just think that they missed a whole market when they ignore that [space in the market]. It's something that us as women ... we have our menstrual cycles every month," she said.

And there are more companies in this market - there's Knockout Panties, Lunapads, and more, proving that this may be the next big thing in lingerie. 

"I think it's more of just, now, having that option of having something. And now that we have it, now you know, we're women. Women are strong. We know what we want," Etienne said.

Maybe it's not particularly sexy, but the people buying this underwear don't seem to mind, and Etienne thinks this new wave of underwear is just beginning. 

"I think it's actually just started," she said.