Our new paper “Li Penetration in Ceramic Solid Electrolytes: Operando Microscopy Analysis of Morphology, Propagation, and Reversibility” is published in Matter. We demonstrate 1) Multiple morphologies of Li penetration are observed; 2) The Li within these structures can be reversibly cycled; 3) The most common Li filaments propagate by a mechanical crack-opening mechanism; 4) The dynamic evolution of filament morphology can be correlated to voltage signatures. [link]