Core C: EM and Mass Photometry Structural Core Project Summary Abstract This is a renewal application of a long-standing P01 grant. Core C provides support for structural studies including routine and advanced transmission electron microscopy, cryo-EM, cryo-shadowing (a technology not available anywhere else) and the novel transformative technology of Mass Photometry. Members of the program project have direct access to this support through routine day to day analysis of samples and also in-depth research projects carried out between members of the core and members of the program project groups. The expertise of the Griffith laboratory in herpesvirus studies augments core C studies.