More tornadoes touch down in America than in any other country, and they are often deadly. So understanding the destructive phenomenon is crucial to helping save people's lives. "Tornado Alley" uses computer graphics in addition to interviews with scientists and survivors of the events to explore the natural disasters from multiple angles. The program also shows the twisters in action, with user-generated content to illustrate how damaging they can be, and it features episodes devoted to cities -- including Moore, Okla., and Joplin, Mo. -- which were devastated by the whirlwinds.