Stephen J. Blundell is a Professor of Physics at the University of Oxford and a Professorial Fellow of Mansfield College, Oxford. He leads a research group which uses muon spectroscopy to solve problems in magnetism and superconductivity and he has been developing ab initio techniques to understand the nature of the muon site. Roberto De Renzi is Professor of Physics at the University of Parma. He started developing muon spin spectrometers at CERN in 1980 and later took part in the design of the ISIS Muon Facility. He currently leads a µSR and NMR group dedicated to the experimental investigation of magnetic and superconducting compounds, and to the application of ab-initio techniques to assist the measurement of condensed matter properties based on the experimental detection of hyperfine fields. Tom Lancaster was a research fellow at the University of Oxford before taking up a lectureship at Durham University in 2012, where he is currently Professor of Physics. His research group's interests include using muons to investigate low-dimensional, topological, and molecular magnetism, and the nature of the muon stopping state. Francis L. Pratt is a senior scientist and STFC Fellow based in the muon group at the ISIS Neutron and Muon Source. He has worked in muon spectroscopy for more than thirty years, using experimental facilities in the UK, Switzerland, and Japan. His research interests are focused on condensed matter physics using muons, with topics ranging from the study of quantum magnets and spin liquids to organic magnets and superconductors and the physics of molecular systems.