Salman Khan is a pioneer of online learning, having founded Khan Academy in 2008. The online educational website features more than 10,000 mini-lectures, free of charge, to anyone in the world. The videos are hosted on YouTube and teach a variety of subjects, such as: mathematics, history, healthcare, medicine, finance, physics, chemistry, biology, astronomy, economics, cosmology, organic chemistry, American civics, art history microeconomics, and computer science. Khan published his international best seller, The One World School House, in October 2012. As of July 2023, the Khan Academy channel on YouTube has 8.17 million subscribers, and its videos have been viewed more than 2 billion times.