Film noir is a cinematic term used primarily to describe stylish Hollywood crime dramas, particularly those that emphasize moral ambiguity and sexual motivation. Hollywood's classic film noir period is generally regarded as stretching from the early 1940s to the late 1950s. Film noir of this era is associated with a low-key black-and-white visual style that has roots in German Expressionist cinematography, while many of the prototypical stories and much of the attitude of classic noir derive from the hardboiled school of crime fiction that emerged in the United States during the Depression.