 In 1946 they moved to Geneva, where Eduard Kellenberger began his doctoral work thesis under the supervision of Jean Weigle, professor of physics at the University of Geneva.Grete Kellenberger contributed to the development of new methods to prepare and analyse biological samples using an electron microscope, a new technique at the time.After Jean Weigle left for the California Institute of Technology in 1948, Grete Kellenberger took on an increasingly important role in the study of lambda phage and its mutations at the University of Geneva.