Before "teenager" became a marketing category, it had to be built by schools, labor law, mass media, and consumer culture. This episode follows the social machinery that separated adolescence from childhood and adulthood: child labor reform, compulsory education, the expansion of high school, youth magazines, pop culture, and the postwar marketplace that learned to sell directly to young people. The story starts with reformers fighting to pull children out of dangerous industrial work, then moves through the high school movement that made adolescence a shared institution rather than a short private transition. From there, the episode tracks how music, magazines, movies, and advertisers turned young people into a visible public audience with its own tastes, anxieties, and purchasing power. Created with Gemini Notebook. The conversation and voices in this episode were generated with Gemini Notebook. Producer note: Gemini Notebook's visibly selected Long output for this episode is 33:07. This is below the normal 45-minute audio release gate and should be treated as an explicit producer-review exception, not a standard-duration pass. Sources consulted include: - A Brief History of Teenagers, The Saturday Evening Post — https://www.saturdayeveningpost.com/2018/02/brief-history-teenagers/ - History of child labor in the United States, part 2: the reform movement, Monthly Labor Review, U.S. Bureau of Labor Statistics — https://www.bls.gov/opub/mlr/2017/article/history-of-child-labor-in-the-united-states-part-2-the-reform-movement.htm - Mass Secondary Schooling and the State: The Role of State Compulsion in the High School Movement, Lawrence Katz / Harvard — https://lkatz.scholars.harvard.edu/publications/mass-secondary-schooling-and-state-role-state-compulsion-high-school-movement - Social Welfare History Project: Child Labor — https://socialwelfare.library.vcu.edu/programs/child-welfarechild-labor/child-labor/ - Social Welfare History Project: National Child Labor Committee — https://socialwelfare.library.vcu.edu/organizations/national-child-labor-committee/ - Teen Worlds: The Emergence of the Teenager, Museum of Youth Culture (source URL not verified; left unlinked) - Teenage: Documentary Features the Stories behind an Invention, American Historical Association — https://www.historians.org/perspectives-article/teenage-documentary-features-the-stories-behind-an-invention-september-2014/ - YouthRules, U.S. Department of Labor — https://www.dol.gov/agencies/whd/youthrules Coverage is curated and limited to sources with matching titles and verified URLs; this is not an exhaustive Notebook source export. Unresolved or omitted Notebook sources include the reCAPTCHA/error rows and Smithsonian, Library of Congress, Time, and DPLA entries unless independently resolved.