‘Subgenres’ explores the different types of documentary that developed. Public affairs documentaries typically take a problem-oriented approach, promising an authoritative, social-scientific view. Propaganda documentaries are made to convince viewers of an organization's point of view. History documentaries face the challenge of representing events for which may be no film. The growth of personal documentary has provoked scholars to explore the relationship of memory to truth. In ethnographic cinema, the balance of power between filmmaker and subject is particularly fraught because the subjects often belong to cultural groups with less influence in society and media. Nature documentaries appear ideologically neutral but actually expose our assumptions about our relationships with our environment.