Although atomic resolution imaging in scanning transmission electron microscopy (STEM) has become standard, greater effort is required when a three-dimensional (3D) structure of the specimen is desired. Tomography typically uses tilt-series with more than a hundred projections to extract a 3D structure. This requires the sample to be stable over long time periods and large doses which is problematic for beam sensitive samples such as 2D materials. These are often only stable for a couple of scans before structural changes occur, especially when one is interested in their defects [4].

Here, we present a new method which is capable of precisely determining the 3D structure of 2D materials with far lower doses [5]. As few as two tilts can provide a 3D structure at better than 30 picometer precision. This is possible because the position of each atom can be reliably tracked when the sample is sufficiently thin. We include simultaneously acquired single side band electron ptychography (SSB) in addition to the ADF signal (Fig. 1). To enable truly rapid scans, a microsecond dwell time capable pixelated camera is employed [6]. The ptychography delivers much higher contrast images, especially at low doses, which enables it to retrieve high quality images with less damage inflicted on the material. Crucially, it also enables accurate location of light elements even next to heavy elements as often occurs in newer 2D materials.