A little over six years ago, hedge fund manager Sal Khan began tutoring his cousins long distance, with the help of a speakerphone and Yahoo Doodle software. By 2006, his tutorials had taken the form of YouTube videos, which Khan made free to anyone who wanted them. Today, people watch Khan's 1,800 tutorials � which cover math and science topics from trigonometry to cosmology in roughly 15-minute chunks � an average of 70,000 times per day. Support to continue the tutorials is coming in from high-profile entrepreneurs and philanthropists, including Bill Gates. Sal Khan joins us today to talk about his passion for education, and what he sees as his program's next steps.