Interactions between plant cells and microbial pathogens involve highly dynamic processes of cellular trafficking and reorganization. Substantial advances in imaging technologies, including the discovery and widespread use of fluorescent proteins as tags as well as advances in laser-based confocal microscopy have provided the first glimpses of the dynamic nature of the processes of defense and pathogenicity. Prior to the development of these techniques, high resolution imaging by electron microscopy gave only a static picture of these dynamic events and live cell imaging was significantly limited in resolution as well as the availability of relevant stains and markers. The incorporation of fluorescent protein fusions and laser-based confocal microscopy into studies of plant–microbe interactions has opened the door to fascinating new questions about the cellular response to attempted infection. Additionally, studies of cellular responses to pathogen infection may lead to new knowledge about fundamental processes in plant cells, such as mechanisms underlying subcellular trafficking and targeting of proteins and other molecules.