Nuclear Pore Complexes (NPCs) represent the exclusive passageway in and out of the nucleus but also function in gene regulation and nuclear organization. NPCs serve as docking sites for many viruses and were associated with several human diseases, e.g. leukemia. Understanding the nuclear transport mechanism will have a huge impact on human health research of such diseases. Multiple copies of ~30 different protein components, termed nucleoporins (Nups), form the major building blocks of NPC. Nups are organized as repetitive modules, called subcomplexes. The subcomplexes, in turn, form the scaffold of NPC in an unknown arrangement. Despite their importance, structure determination of NPCs is a considerable challenge, primarily due to their sheer size.To generate an atomic model of the human NPC, data at the different resolution levels have to be systematically collected and integrated. Determining the position of Nup subcomplexes within the NPC will be a critical step to bridge the resolution gap between different structural techniques. Since the precision of 2D-immuno-gold labeling techniques is insufficient to associate individual Nups with distinct features of the NPC structure from cryo-electron tomography (cryo-ET), alternative strategies are needed to achieve this goal. Here I propose to improve the resolution of the human NPC structure to allow assigning subcomplexes into the overall assembly. This will be achieved by cryo-ET, subtomogram averaging and further development of algorithms correcting for NPC plasticity. Furthermore, I will determine the precise positioning of subcomplexes by obtaining 3D structures of NPCs containing tagged Nups. This will contribute significantly to our understanding of the overall organization of the NPC and thus, nuclear tranport mechanism. This proposed project will give me the opportunity to learn new skills, acquire competencies and, thus pave the way towards an independent career.