The Bill & Melinda Gates Foundation announced Feb. 7 that CEO Patty Stonesifer would be leaving the organization by the end of the year. Stonesifer, a former Microsoft executive, has led the foundation since its inception in 1997. In that time she has organized the foundation into three program groups -- Global Health, Global Development and U.S. Programs -- and overseen the issuing of more than $16 billion in grants. Since June 2006 she has been working to incorporate the personal fortune of Warren Buffet into the foundation's endowment, which now stands at $38.7 billion, the largest in the world. Stonesifer will work with foundation co-chairs Bill and Melinda Gates to select a new CEO.