Payal Kadakia, an avid dancer since the age of 3, had a hard time finding dance classes in New York City.

So, in 2011, she launched Classtivity, an online search engine kind of like OpenTable, but for fitness. There was only one problem… no one was using it.

She pivoted and rebranded to ClassPass, an app-based subscription that allows users to try classes from tons of locations, from yoga studios to boxing gyms, without having to buy separate memberships.

Since then, fitness junkies in 31 US cities have booked over 20m classes through the app, the company’s raised over $84m, and were predicted to do over $180m in sales in 2016.