Thrilled to be joining the @twitter board. It's transformed the media and the world like few other things in history (and continues to)!! — Debra Lee (@IamDebraLee) May 16, 2016

In the past, Twitter has been criticized for being both too white and too male, and its previous attempt to hire a new head of diversity didn't exactly shift that perception at all. As civil rights leader Jesse Jackson pointed out last December, "Blacks and Latinos over-index on using Twitter, but their board of directors and C-suite leadership remain all white." As Lee takes her seat on the board, however, two other execs -- venture capitalist Peter Currie and media mogul Peter Chernin -- are stepping down. In April, the company also added Pepsico VP/CFO Hugh Johnson and British entrepreneur Martha Lane Fox to the board.