Engineers are masters of scale. They harness energy from the sun, wind, rivers, atoms, and ores. They manipulate electrons, photons, and crystals to compute and communicate. They devise instruments that detect perturbations in the fabric of space-time. And they grapple with challenges—anticipated or not—that are presented by the scale of the problem they are trying to solve. The articles in this issue describe engineers who think about, interact with, and create things at very precise and...
