Recorded video lectures contain frequent quizzes that reinforce concept retention as well as deeper assignments that test students' understanding and build mastery of the material. The Coursera platform also offers community forums that encourage students to participate actively with classmates from around the world. Coursera was founded in the fall of 2011 by Stanford Computer Science Professors Daphne Koller and Andrew Ng. It builds on the groundbreaking technology they helped develop that was used to host Stanford's free online classes. These classes were an instant success, receiving more than 350,000 enrollments across 172 different countries. "Our mission is to teach the world and make higher education available for everyone," said Coursera co-founder Andrew Ng. "By partnering with the world's leading universities, we're making college-level classes more accessible to anyone who wants to learn," added Daphne Koller.