Inspired by an artist’s stencils, researchers have developed atomic-level precision patterning on nanoparticle surfaces, allowing them to “paint” gold nanoparticles with polymers to give them an array of new shapes and functions. The “patchy nanoparticles” developed by University of Illinois Urbana-Champaign researchers and collaborators at the University of Michigan and Penn State University can be made in large batches, used for a variety of electronic, optical or biomedical applications, or used as building blocks for new complex materials and metamaterials.