In Monsters, Inc., the company originally collects screams from children to produce energy.
The factory sends trained scarers through magical closet doors into children’s bedrooms. Their task is to frighten the children, capture the resulting screams in canisters, and deliver those canisters to the company’s energy-processing system. The monsters believe screams are the most effective energy source at the start of the film.
The central conflict changes this assumption. After Boo enters the monster world, Sulley discovers that her laughter is powerful and harmless. Monsters, Incorporated eventually changes its operation from collecting screams to generating energy through laughter, turning the film’s scare-based economy upside down.
Screams are therefore the original fuel source, while laughter becomes the replacement. Tears and dreams are not the company’s established energy products. The canisters and scream-processing machinery are important visual parts of the factory’s industrial design.