Optical and electron microscopy are indispensable tools for nanoscale imaging of proteins and cell membranes. In principle, it should be possible to use the electron beam both for ultrastructural imaging using electron scattering and for protein localization by directly exciting suitable protein tags and detecting their luminescence – a process termed cathodoluminescence (CL). I will discuss our efforts on developing new imaging strategies to achieve reliable multicolor detection of single ~10 nm cathodoluminescent lanthanide nanocrystals (cathodophores). These nanocrystals are promising candidates for protein labeling in multicolor electron microscopy. In the future, cathodophores can be used to understand the fascinating cell biology of membrane-associated structures that drive various cellular processes, including transmembrane signaling and protein trafficking.
