The power of films in the imaginative lives of audiences can only be properly understood when films are located within the wider cinema culture. These comprised fan magazines, cigarette cards, postcards, cheap biographies, the book of the film, the sheet music of the film and above all radio. But during the 1930s, Hollywood began to appreciate the value of radio in publicizing and promoting its films. It discovered that radio complemented films rather than substituted for them. For three decades in both the United Kingdom and the United States from the 1930s to the late 1950s radio was the dominant medium for the daily domestic consumption of news, music and drama. The major structural development in the 1920s was the emergence of national networks: the National Broadcasting Company (NBC), initially two networks, Red and Blue, in 1926 and the Columbia Broadcasting System (CBS) in 1927.