It began with a smoke break. James Monsees and Adam Bowen were two ambitious graduate students at Stanford, and in between puffs after class they dreamed of a way to quit smoking. Their solution became the Juul, a sleek, modern device that could vaporize nicotine into a conveniently potent dosage. The company they built around that device, Juul Labs, would go on to become a $38 billion-dollar company and draw blame for addicting a whole new generation of underage tobacco users.