As smoking’s popularity plummets, vaping is on the rise. People have turned to e-cigarettes and other products to get a fix of nicotine, THC, and other flavored vapor. For companies like Juul, the industry is booming, and regulators at groups like the Food and Drug Administration have struggled to craft regulations to keep up with the rising demand. In the United States, young people, in particular, have started vaping in droves, leading the surgeon general to declare youth vaping an epidemic in 2018. An outbreak of a mysterious lung injury linked to e-cigarette use (particularly in people who use THC) has also captured the attention of both regulators and public health officials.