Solid state physics is a complex area which needs a full arsenal of experimental techniques to uncover all its intriguing aspects. The present book presents selected results from a couple of methods where phenomena in solids are observed from points of view that fall somewhat outside the experimental mainstream, but have contributed with unique information to the understanding of magnetism, supercondivity, point defects in metals, surface and interface physics and
the physics and chemistry of metal/hydrogen systems, in particular diffusion phenomena. The PAC and uSR methods described here are based on the observations of local magnetic and electric fields and
their dynamic behaviour by recording the spin motion of excited nuclei and implanted positive muons, respectively; another method utilizes the electrostatic interaction of protons for the study of metallic multilayers and their interfaces. The text is centered on the relevant physical problems rather than being method-oriented and puts the specific, and sometimes unique, information gained by the above mentioned methods into a general perspective.