Electron microscopy of proteins, DNA and other macromolecules has recently advanced to the point where near-atomic-resolution structures can be obtained without the requirement of crystallization or labeling of the specimen. Instead, individual copies of the macromolecule of interest are imaged in a layer of vitreous ice, and the resulting “single particle” images are analyzed to determine the orientation of each particle. Combining information from a set of 104 to 105 particle images, one can now obtain a 3D density map in which details at 3 Å or smaller scales can be resolved. I will describe the technical developments that have made possible this advance in resolution, and will discuss work in my laboratory on structures of membrane proteins using this technique.