What historical or cultural knowledge do you need to teach your readers about the ages (s) of adulthood?

Basically, the knowledge base to teach about adulthood is the meaning or definition. Legally adulthood is defined by majority of age. In truth adulthood is reached gradually by maturing and, most importantly, becoming independent from the original family, emotionally and financially. Maturity signifies to be able to be fully responsible for one's relationships, thoughts, actions and life as a whole.