40 million Americans — and over a billion people worldwide — still smoke. Can disruptive technologies curb the public health risks associated with smoking? Are vaping, heat sticks and other nicotine-delivery systems really safer than tobacco? When it comes to tobacco harm reduction (THR), what are the trade-offs? How should THR technologies be regulated? Do they raise other policy concerns, such as privacy? And what lessons should we draw for public policy writ large?