In film theory, genre refers to the method of film categorization based on similarities in the narrative elements from which films are constructed. Fictional films are usually categorized according to their setting, theme topic, mood, or format. The setting is the milieu or environment where the story and action takes place. The theme or topic refers to the issues or concepts that the film revolves around. The mood is the emotional tone of the film. Format refers to the way the film was shot (e.g., anamorphic widescreen) or the manner of presentation (e.g.: 35 mm, 16 mm or 8 mm).