"It used to be so simple," Katie Couric says in National Geographic Channel's documentary Gender Revolution: A Journey with Kaite Couric, "you were either a boy or you were a girl. But that was then. And this is now."

As the trailer shows, the documentary takes on what gender means in 2017 — and not just the conversation about transgender people (and where they should use the bathroom) that's taken place in recent years. In line with the magazine's print issue of the same name that's been one of its most popular ever, the doc explores gender in totality: social roles, brain chemistry and more.

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Among those featured are Vanessa and JR Ford, whose 5-year-old transitioned from a boy to a girl; Georgiann Davis, born with male and female organs; and Michaela Mendelsohn, a trans activist and business owner. "We're a lot more complicated than we've assumed," Couric said at the Television Critics Association winter previews Friday. "We're learning so much about what defines us and what factors go into that."

Gender Revolution premieres Monday, Feb. 6 at 9/8c on National Geographic Channel.