A new documentary called Teenage is out today, by 31-year-old filmmaker Matt Wolf. It may be surprising to learn that our concept of teenagedom—the state of existence between being a child and an adult—is a relatively new one, born from a post-war culture that campaigned to eradicate child labor and where fleeting fads like Bright Young Things glamorized that ephemeral moment of our life, being no longer young but not yet old.