A thriller is a genre of film that uses suspense, tension, and excitement to stimulate the audience's emotions. Thrillers keep audiences on the edge of their seats as the plot builds to a climax. There are many types of thriller films, including comedy thrillers, crime thrillers, psychological thrillers, and supernatural thrillers. Key themes in thrillers include ransoms, revenge, kidnappings, stalking, and paranoia. Alfred Hitchcock is considered a famous director of thrillers, having made films like Psycho, The Birds, and Vertigo that followed thriller conventions of tension, pacing, lighting, protagonists, and suspense.