Energy touches virtually every aspect of public policy. Dramatic revolutions in U.S. shale oil and gas supply over the last decade and their massive economic benefit have shown that energy production is a major contributor to job creation, investment, and economic growth. The electric power grid, which supplies nearly half of all the energy ultimately used in the country, is a prime target for terrorist attack; thus, policies surrounding the grid are a central element of homeland security strategy, since reliable electric power is essential to water supply, sewage treatment, traffic control, computer servers, national security infrastructure, and so much else in modern society. Energy is also central to foreign policy. Large revenues—especially from oil sales—often flow to overseas energy producers who can enrich malicious governments and non-state actors, giving them capabilities to harm U.S. interests. One of today’s greatest policy challenges—the threats of unchecked global warming—is an intrinsically foreign problem, as the buildup of greenhouse gases in the global atmosphere has arisen from how the whole planet has used and depended upon carbon-based fossil fuels.