Rich Sullivan, who held top finance roles at Twitter, STX Entertainment and DreamWorks Animation, was named chief financial officer of saving and investing app Acorns as it preps for an IPO.

The app – full name Acorns Grow – has more than four million subscribers and has helped them invest over $9.6 billion, among the the largest subscription services in U.S. consumer finance.

Sullivan joins Acorns from Twitter where he led corporate finance and financial planning and analysis. Previously, he held executive positions at STX Entertainment and DreamWorks Animation, where he served as deputy CFO. He’s also held various roles at AT&T.

“Rich brings a unique combination of expertise, vision, and commitment to mission,” said Noah Kerner, CEO of Acorns. “Our next phase of growth as a company will only be fueled by his leadership.”

Sullivan called Acorns a company “at the cross section of technology, financial services, and social responsibility. I look forward to working with the team as we continue to empower more investors, and do so with their financial best interests in mind.”

In May, Acorns announced plans to go public by combining with Pioneer Merger Corp., a publicly traded SPAC, or special purpose acquisition company.

Its current CFO, and former PayPal exec, Jasmine Lee will overseeing day-to-day operations as chief operating officer.