Bill Gates is famous for co-founding Microsoft in 1975 and turning it into the company that put a PC on nearly every desk, which made him the world's richest person for a record 18 years. Since stepping back from Microsoft, he's become just as well known for the Bill & Melinda Gates Foundation — the world's largest private charitable foundation, which has helped save more than 80 million lives through vaccine and disease-eradication programs and is now spending down its entire endowment by 2045.