My PhD research resulted in a first principles approach to the computation of energy loss near edge structure (ELNES). Recent advances in energy loss resolution, computational resources and structural prediction, mean that its latest incarnation (OptaDOS) is increasingly used in the microscopy community. With Francesco Mauri, I went on to develop a quantitative theory for the prediction of magnetic response in the solid state, applicable to the whole periodic table. Based on our gauge including projector augmented waves (GIPAW) it enables the prediction of nuclear magnetic resonance (NMR) chemical shifts, quadrupolar coupling constants, J-coupling constants, electron paramagnetic resonance (EPR) g-tensors and hyperfine parameters. It has revolutionised the interpretation of solid-state NMR spectra, and is an integral part of " NMR Crystallography".