With the success of An Inconvenient Truth, a movie about former U.S. vice president Al Gore's campaign to educate the public on global climate change, long-form documentaries, particularly those concerning environmental issues, are enjoying a renaissance. These films can be a powerful educational tool because they create teachable moments by heightening students' interest in environmental topics. Successful documentaries engage the audience emotionally and tell a compelling story, with heroes and villains. Often films touch on some scientific concepts and may even contain graphics and animations that are useful in explaining processes. However, they generally do not provide a balanced exposition of the science and technical issues that underlie the environmental problems described. Documentaries may advocate a particular policy position.