Do you know the difference between nuclear fission and nuclear fusion? Here's a teacher guaranteed to hold your attention in class. GLaDOS, the hilarious homicidal artificial intelligence from the Portal games, explains the two nuclear reactions in a new video produced by NASA. While she isn't explicitly called GLaDOS in the educational piece, the credits leave no doubt that voice actress Ellen McLain is reprising her role. (You might remember her recent stint in Guillermo del Toro's Pacific Rim as well.) For an educational, entertaining look at the basic principles, not to mention her latest plot to take over the world, be sure to listen closely to NASA's Official Talking General Leisure and Diversion Operational Server (aka NOTGLaDOS) in the following video.