Massive open online courses (MOOC's) are the latest development in online education. Over the past decade, millions of students have taken free online versions of existing courses at well-known universities like the Massachusetts Institute of Technology, but such courses often offered little more than reading lists and lecture notes. MOOC's are typically free, but they are far more interactive, interspersing quizzes and other assignments among short videos. Given the courses' huge size, exchanges between the professor and students are minimal. But many MOOC's feature automated grading and the ability to earn a certificate for mastering the material. More than 1.3 million students have already signed up for MOOC's through Coursera, a for-profit company founded by two Stanford University computer scientists. A handful of other providers, such as Udacity and Udemy, which are also for-profit, and edX, a nonprofit effort run jointly by MIT, Harvard University, and the University of California at Berkeley, are rapidly adding courses. With best practices yet to be established, anything goes, and different professors take different approaches.