Robinhood Markets Inc., the California-based financial services firm that offers retail investors a simple stock trading experience via its iPhone and Android app, is aiming to rival the likes of Coinbase, by further expanding into cryptocurrency trading.

Following a successful February launch of its cryptocurrency trading offering, which allows retail investors to buy and sell the cryptocurrencies Bitcoin and Ethereum in only ten US states, Robinhood has announced a $363 million series D funding round that will allow it to expand its crypto service across the rest of the US by the end of 2018.

The investment round pegs Robinhood’s valuation at $5.6 billion, making it the second most valuable private finch startup in the US after Stripe, the online payments firm. Robinhood’s valuation has nearly quadrupled from the $1.3 billion valuation it received a year ago after the previous round of fundraising. The company doubled its brokerage accounts within that year to more than 4 million, beating its next closest rival E*Trade which had 3.7 million brokerage accounts.

The Series D round of funding was led by DST Global, with participation from new investors such as Capital G, Sequoia Capital, Kleiner Perkins, and Iconiq Capital.

Robinhood Co-Founder and Co-CEO Baiju Bhatt explained to Fortune why he thinks the Series D funding was so successful:

“I think the real ‘X factor’ that made investors even more excited about being a part of Robinhood was seeing our ability to, with a very, very limited workforce, ship three brand new products in these last six months, while maintaining and growing one of the largest brokerages in the U.S.”

Through the funding, Robinhood says it plans to aggressively expand its cryptocurrency trading service, with Bhatt saying he expects to “be either the largest or one of the largest crypto platforms out there” by the end of the calendar year.

[Image Credit: Robinhood Facebook Page]