The inner membrane of mitochondria exhibits a unique three dimensional structure. It is also exceptionally rich in proteins, most of which facilitate transport and catalytic processes. Currently, it is assumed that the structure of the inner membrane enables dedicated protein and lipid environments resulting in the spatial organization of protein functions. Accordingly, protein function and membrane topology appear to be tightly intertwined with each other in mitochondria. Considering this, it is surprising that we still lack detailed insight into how the inner membrane is shaped. Moreover, information on the actual distribution of protein functions in the inner membrane is very scarce at the best. To this end, experimental approaches that provide temporal and spatial information of inner membrane shape and protein localisations are essential to assess and eventually understand how membrane shape and functional organization are brought about. In this research initiative, we take a decisive step to tackle fundamental questions on mitochondrial ultrastructure and bring together researchers with unique expertise in mitochondrial imaging technologies with scientists addressing central biological questions on mitochondrial functions. We expect that the combination of functional analyses with state-of-the-art microscopy will allow us to obtain a detailed view on the organization of the inner membrane, to address the question on how proteins support the shaping of the inner membrane, and to define how these processes are interconnected and regulated in the cellular context.