Bill Gates is a technologist, business leader, and philanthropist. In 1975, he cofounded Microsoft with his childhood friend Paul Allen. Today, he is cochair of the Bill & Melinda Gates Foundation, where he has spent more than 20 years working on global health and development issues including pandemic prevention, disease eradication and water, sanitation and hygiene. He is also the founder of Breakthrough Energy, an effort to commercialize clean energy and other climate-related technologies. Bill has three children.