Lululemon has joined in a just completed $34 million Series B funding round for a New York-based high-tech fitness start-up, Mirror, which launched a smart full-length LCD mirror in September of last year. The display can be used as an interactive home gym, with live and on-demand fitness classes.

Taking a minority share in the venture, Lululemon will use the mirrors to bring new content to its interactive classes, including meditation classes hosted by brand ambassadors. When switched off, the screen acts as a regular mirror; when switched on, users can see both themselves and a digital instructor, allowing them to stream unlimited classes ranging from boxing to yoga.

Lululemon started to use smart mirrors in 2015, when the Canadian athleisure company tested mirrors developed by a Calgary-based company, Nobal Technologies, in two of its flagship stores in Canada and the U.S. as a “digital community board.”

For Mirror, this was the third round of financing to have been announced, with a total of $75 million raised in almost 20 months, led by Steven A. Cohen’s Point72 Ventures and the investment firm Lion Tree. Other investors in Mirror include Spark Capital, the seed-stage venture capital fund Lerer Hippeau, and the American model Karlie Kloss.

The smart mirror trend started about five years ago. Ralph Lauren, for example, introduced the interactive mirrors supplied by a San Francisco-based retail technology platform, Oak Lab, in its New York City flagship store in 2015. The mirrors were placed in the fitting rooms. During the fitting, the mirror recommends clothes and accessories to the customer to complete the image. If the buyers are not ready to make a purchase on-site, they can choose to send information about the product to their mobile phone. According to company representatives, sales increased three times after Ralph Lauren opened the smart fitting room, and customers started spending more time in the store. Similar mirrors can also be found in Puma’s new flagship store in New York City, Adidas’ store in London and in several other retail locations worldwide.