According to the most extensive scientific report on the subject so far, gathered by the National Academies of Sciences, Engineering, and Medicine at the request of the FDA, the answer is—well, both. Maybe. On the one hand, it seems clear that on several metrics the electronic products are better for one's health than combustible cigarettes, and there's evidence that they can help some adult smokers quit. On the other, there is strong evidence that vaping appeals to kids and teens, and the new report finds that these users often progress from e-cigs to combustible cigarettes. With just a decade of data on e-cigarette use, we have no way of knowing how lifelong vaping habits will affect the health of these young people, which is to say nothing of the obvious health effects they'll suffer if they turn to traditional smoking instead.