"I am investing in several ideas outside the foundation" Bill Gates noted in the annual Gates Foundation letter.
So where is one of the the worlds richest men investing his own money since leaving Microsoft?
Energy technology is one sector, an area where Gates has indicated he is spending a great deal of effort.
In the interview below, Gates told a reporter that he invested $20 million in Vinod Khosla's green business fund.
Author: CNET Video
