For those of you who thought Youtube videos were simply an endless resource of mindless entertainment, or a welcome diversion from your studies, think again. The site is the birthplace of the world’s largest free online school – which started purely by chance.

Salman (Sal) Khan lives in California. He was a stellar student and valedictorian of his high school. With a MBA from Harvard Business School and a BS in Mathematics from MIT, he’s always been a hard-working learner with little time to play around and watch Youtube videos. He had a lucrative career in hedge funds, but that all changed when he discovered the power behind his passion for teaching.