In a fashion world trend known as “athleisure,” clothes that can work at the gym…can also make a fashion statement.

“Leggings and tank tops and sneakers are sort of taking over the style masses,” says Wall Street Journal reporter Elizabeth Holmes. “But you don’t actually have to work out in them. For a lot of people this is just sort of their everyday casual look.”

Popular brands such as Lululemon started making yoga pants outside-of-yoga-class stylish, and high-fashion brands put sneakers and sweatshirts on the runway.

“Suddenly all these different parts of the fashion food chain are participating in the same trend,” Holmes says. “So that’s sort of why we see this ‘peak athleisure’ moment.”

Now this moment has become a big business — Bergdorf sells some leggings for more than $400.

“Women are justifying this purchase by saying ‘Hey, this is not just something I’m going to sweat in, but it’s something I’m going to brunch in.’” Holmes says.

And it isn’t just luxury brands; athletic brands like Under Armour and Adidas are capitalizing on athleisure.

“Every apparel brand out there sees a piece of this pie,” Holmes says. “So if you’re a performance-based company like Nike you can infuse a little more fashion and suddenly attract a broader customer base. Or if you’re a fashion brand, you think ‘Hey, I can make something in spandex!’”