The Khan Academy is a not-for-profit organization on a mission with the goal of changing education for the better by providing a free world-class education for anyone anywhere. All of the site's resources are available to anyone free of charge.Khan academy library of videos covers K-12 math , science topics such as biology, chemistry, and physics , and even reaches into the humanities with playlists on finance and history . Each video is a digestible chunk, approximately 10 minutes long, and especially purposed for viewing on the computer. For more details please visit http://www.khanacademy.org