Pre-Code sex films refers to movies made in the Pre-Code Hollywood era between the introduction of sound in the late 1920s and the enforcement of the Motion Picture Production Code in 1934, which contained sexual references and images that were contrary to the yet to be enforced Hays Code. Pre-Code sex films explored women's issues and challenged the concept of marriage, and aggressive sexuality was the norm. The sexual subject matter of the uncensored period was found within many movie genres, most especially in dramas, crime films, exotic-adventure films, comedies and musicals.