In the project, we will study solution dynamics, photoinduced dynamics, electronic structure and hydrogen bonding in both fundamental investigations and for the purpose of energy-related applications such as photocatalysis and solar cells. Ab initio molecular dynamics (AIMD) simulations, quantum chemical calculations and spectral simulations are performed for the interpretation of spectroscopic data to investigate electronic structure and ultra-fast dynamics in solution and photoinduced processes. A continuous interplay between theory and experiment acts as a stimulus for method development. With a combination of multi-configurational methods for spectrum simulations, dynamic sampling with AIMD simulations and machine-learning excited-state dynamics, we can simulate both time-resolved spectra and intrinsic dynamical effects in resonant inelastic X-ray scattering. Guided by experiment and for the guidance of future experiments, I propose to simulate hydrogen bond dynamics in electrolyte solutions, excited-state dynamics in gas phase and solution, and dynamics in solar cell materials. On the basis of the AIMD simulations, we can model X-ray and electron spectra containing information on electronic structure, excited-state molecular dynamics and molecular interactions. In some cases the simulations are also used to model vibrational spectra, in order to investigate hydrogen bond dynamics and to create a theoretical link between different experimental probes.