Retired Chair of Physical Chemistry, University of Stuttgart, and Retired Extraordinary Professor, Chemistry Department, University of Pretoria Emil Roduner has worked in various fields of physical chemistry, with a focus on muonium chemistry, proton conductivity, and degradation of polymer electrolyte fuel cells, nanomaterials, and electrocatalytic conversion of CO2 to liquid solar fuels. A more recent focus is on selected long-standing problems of the description of matter and processes.