Pushing sensing technologies into previously inaccessible domains is one of the great challenges in physics. Our group’s research is aimed at developing sensors that can image magnetic and electric fields with high sensitivity and nanoscale resolution. This allows us to investigate phenomena occurring at a scale that cannot be interrogated by previously established techniques. In particular, we use the Nitrogen-Vacancy center in diamond as our sensing tool. We consider how these sensors can be improved, leading to work in a wide variety of topics. These include research in quantum optics to improve the photon collection efficiency, and hence accuracy, of the NV spin readout, along with fundamental investigations on how mechanical oscillations can be coupled to the NV center spin, which could lead to higher-precision sensing schemes as well as the generation of complex quantum states. Through the development of these sensing tools we have been able to image superconductors, magnetic materials, and nanoscale devices at a previously unexplored resolution.