"Monsters, Inc. is a 2001 computer-animated film and the fourth feature-length film produced by Pixar Animation Studios. Monsters, Inc. is the main power utility in Monstropolis, a monster-populated city; the company uses the power of human children screams scared by its employees, who enter their rooms through closets linked to special doors on the company's scarefloor, to generate the city's power. However, due to children becoming desensitized, the company finds itself struggling to meet the power needs of Monstropolis.
Source: Wikipedia, "Monsters,_Inc.", available under the CC-BY-SA License.