Steven Chu was the Secretary of Energy until 2014 – the first time that a scientist had served as a member of the president’s cabinet. He won a Nobel Prize in physics in 1997 for his work on cooling and trapping atoms with laser light; after finishing his term as secretary, Chu went back to the lab bench. In this interview, Chu talks about his latest research; some of the reasoning behind the decisions he made in office; what policymakers need to do to encourage investment in renewables; what frustrations he had in trying to promote energy efficiency; and how to make progress in the current, anti-regulatory political environment.