This is a video guide that accompanies Modern Marvels Greatest Inventions. I use something like this when I need a break or if I have a sub. This viewing guide is free because it is simply a list of the inventions from the video. The students write at least one complete sentence about each video. Modern Marvels videos can be found on the History Channel or the videos can be purchased online. Each video usually sells for $19.99. These videos are perfect when you have a substitute because the videos last about 45 minutes.