New presidents typically move into the White House neither expecting to spend much time on scientific issues, nor prepared to. But history shows that, ready or not, every president ends up grappling with a host of science-related policy issues or crises. Climate change is sure to loom large, as will the annual debates over how much the government should spend on basic research and help industry commercialize new discoveries. Technological advances, from self-driving cars to new genetic-engineering techniques, will pose new regulatory challenges. And there are likely to be unplanned events, such as disease outbreaks, oil spills, and natural disasters.