With 1968 would come the adoption of the MPAA rating system, which was an attempt to allow filmmakers to make the movies they wanted, with language, and violence and nudity if they so chose, while still preventing children from being exposed to material that was deemed inappropriate. With this came some sort of structure as it regards nudity in film and what was acceptable for whom, but the organization has never been entirely transparent and so we're left to guess based on the movies that we get what is acceptable and what is not. For example: Nudity associated with sex is sure to get you an R-rating, but nudity all by itself can be acceptable in PG-13 movies, like Titanic.