Free stock trading app maker Robinhood Market Inc. is raising $350 million in a late-stage round that brings its valuation to a stunning $5.6 billion.

The Series D round was led by DST Global, according to a report Thursday in the Wall Street Journal.

Robinhood, founded in 2013, rose to fame by offering the first and now most popular zero-fee stock trading app, often cited as being beloved by millennials. But the company has moved forward to launch a website service as well in November, then adding support for cryptocurrency trading, albeit in somewhat limited form, in January.

The app is said to have 4 million users across both its stock and cryptocurrency trading platforms, most of which overwhelmingly fall into the “millennial” age category of roughly 18- to 35-year-olds, according to CNBC. By comparison, Coinbase Inc., the leading U.S. cryptocurrency exchange, is said to have more than 10 million users but a valuation of only $1.6 billion as of its last round in August.

Greylock Partners, one of the famous Sand Hill Road venture capital firms, is also an investor in the company. Partner Josh Elman took the role of vice president of product at Robinhood earlier this week.

If the round goes through as reported, Robinhood will take its total amount raised to $526 million. Previous investors include Index Ventures, Andreessen Horowitz, GV (Google Ventures), Slow Ventures, LocalGlobe, Thrive Capital, QueensBridge Venture Partners, Rothenberg Ventures, Social Leverage and a number of individual investors, most notably Tim Draper, Dave Morin, Jason McCabe Calacanis and, not least, Snoop Dog.

Image: Robinhood