Measuring 3D atomic coordinates in materials has been a driving force behind many scientific and technological advances. Techniques such as X-ray crystallography are powerful tools to measure average atomic positions, but cannot identify individual, atomic-scale defects which can strongly influence a material’s behavior, particularly in the case of nanomaterials. A single image from a high resolution electron microscope can measure crystal lattices, defects, and strain, but only in two dimensions. Recent developments in electron tomography have extended this atomic resolution local characterization to three dimensions. This method has been used to isolate crystalline grains in 3D, to visualize the atomic arrangement of atoms in defects, and to localize individual atoms of a sample with 20 pm precision. From the measured atomic coordinates, 3D dislocation and strain fields can be determined and related to the surface conditions of the sample, while in samples with more than one atomic species, chemical ordering can be mapped in 3D with single atom sensitivity. Critical to the success of this project have been cutting edge instrumentation and algorithmic developments. This colloquium will emphasize the technologies that underpin this exciting new capability.