The Advanced Research Projects Agency for Health (ARPA-H) seeks proposals for the Restorative & health-Enhancing Sleep Time (REST) program, a bold effort to transform how poor sleep is measured and treated by enabling objective, home-based, closed-loop technologies that detect health-relevant sleep microstructures and respond to them in real time. If successful, REST will establish the technical foundation for a new generation of sleep health technologies that are objective, personalized, and capable of improving long-term health outcomes at scale.