In memory of four pioneers in the field of grain boundaries (GBs) and Interfaces, who recently expired: Jany Thibault-P,nisson (aEuro 2011), Pierre Delavignette (aEuro 2011), Claude Goux (aEuro 2012) and Jacques L,vy (aEuro 2012), I recall some of their major achievements. Jany Thibault-P,nisson was a pioneer in the use of High Resolution Transmission Electron Microscopy. She studied dislocations in Germanium with Alain Bourret in Grenoble, then GBs in Ge and Si, their structures and their interactions with extrinsic dislocations under plastic deformation, and finally interfaces in metallic multilayers. Pierre Delavignette also was a marvellous electron microscopist who worked on dislocations in non-metallic multilayered structures with Severin Amelinckx in Mol (Belgium), and on GBs in hexagonal metals, for which he contributed to the extension of Ranganathan's approach, together with George Bleris, Theodoros Karakostas, G,rard Nouet, Serge HagSge and others, in parallel with Hans Grimmer, David Warrington, Walter Bollmann, and Roland Bonnet. Claude Goux developed a school of processing, observation, and atomistic simulation of GBs in very pure metals, bringing to the A parts per thousand cole des Mines of Saint-A parts per thousand tienne what he had learnt in Vitry under Georges Chaudron in the late 1950s. He also had a strong taste for modelling, and his impulse culminated with the 1975 Conference on GBs in Metals held in Saint-A parts per thousand tienne. Jacques L,vy has been one of Goux's first Ph.D. students. They probably made the first electron microscopic observations of high-angle GBs around 1966. Jacques L,vy rapidly exerted to assume important positions and became, for instance, the Director of the A parts per thousand cole des Mines of Paris. Despite all his responsibilities, he still attended IIB conferences many times.