My laboratory uses in situ structural biology techniques to study how prokaryotic cells interact with their environment, important for several fundamental processes including adhesion and biofilm formation. We use electron cryomicroscopy (cryo-EM) and tomography (cryo-ET) to resolve structures of molecules directly at the prokaryotic cell surface. Correlated light and electron microscopy (CLEM) and mass spectrometry (MS) are used to support our investigations. We combine in vitro reconstitution of key molecules with in situ imaging to understand the structure of molecules at surface of prokaryotic cells at the atomic level, facilitating our understanding of how cells interact and respond to environmental stimuli. In my talk I will discuss how Pseudomonas aeruginosa bacteria form biofilms to evade antibiotic treatment, with some ideas on blocking these processes. I will also show how the latest cryo-EM imaging can help unravel fundamental mechanisms pervasive across pathogenic bacteria.