Teenagers didn't always exist. They had to be invented. As the cultural landscape around the world was thrown into turmoil during the industrial revolution, and with a chasm erupting between adults and youth, the concept of a new generation took shape. Whether in America, England, or Germany, whether party-crazed Flappers or hip Swing Kids, zealous Nazi Youth or frenzied Sub-Debs, it didn't matter - this was a new idea of how people come of age. They were all "Teenagers." This hypnotic rumination on the genesis of youth culture from the end of the 19th century to the first half of the 20th, is a living collage of rare archival material, filmed portraits, and diary entries read by Jena Malone, Ben Whishaw, and others.