Cryo-electron microscopy (cryo-EM) is a key imaging modality for studying the structures of macromolecular complexes in their physiological environment. In the cryo-EM group we aim at a structural understanding of processes associated with cellular membranes. To this end we make use of single particle cryo-EM and in particular cryo-electron tomography (ET) approaches. While single particle cryo-EM is an excellent approach to study isolated complexes at near-atomic resolution, cryo-ET allows imaging complexes in their native settings, such as organelle and plasma membrane. We actively develop methodology for in situ structural biology and apply it to understand processes such as membrane-associated protein biogenesis and host-pathogen interactions.