According to The Wall Street Journal:
Zuckerberg Initiative’s first investment will be $600 million to create a research lab of engineers and scientists
Dr. Chan announced the $3 billion investment during an event in San Francisco attended by many of Silicon Valley’s elite, including Facebook Chief Operating Officer Sheryl Sandberg and CEO of Alphabet Inc.’s Google unit Sundar Pichai. Microsoft Inc. founder Bill Gates, whom Mr. Zuckerberg described as a mentor for decades, also spoke.
Zuckerberg is only 32 years old, so I guess Gates started mentoring him in high school!