The properties of nanomaterials are essentially determined by their 3D structure. Electron tomography enables one to measure the morphology and composition of nanostructures in 3D, even at atomic resolution. Unfortunately, all these measurements are performed at room temperature and in ultra-high vacuum, which are conditions that are completely irrelevant for the use of nanoparticles in real applications! Moreover, nanoparticles often have ligands at their surface, which form the interface to the environment. These ligands are mostly neglected in imaging, although they strongly influence the growth, thermal stability and drive self-assembly. I will develop innovative and quantitative 3D characterisation tools, compatible with the fast changes of nanomaterials that occur in a realistic thermal and gaseous environment. To visualise surface ligands, I will combine direct electron detection with novel exit wave reconstruction techniques. Tracking the 3D structure of nanomaterials in a relevant environment is extremely challenging and ambitious. However, our preliminary experiments demonstrate the enormous impact. We will be able to perform a dynamic characterisation of shape changes of nanoparticles. This is important to improve thermal stability during drug delivery, sensing, data storage or hyperthermic cancer treatment. We will provide quantitative 3D measurements of the coordination numbers of the surface atoms of catalytic nanoparticles and follow the motion of individual atoms live during catalysis. By visualising surface ligands, we will understand their fundamental influence on particle shape and during self-assembly. This program will be the start of a completely new research line in the field of 3D imaging at the atomic scale. The outcome will certainly boost the design and performance of nanomaterials. This is not only of importance at a fundamental level, but is a prerequisite for the incorporation of nanomaterials in our future technology.