Harald Oberhofer - Technical University Munich (TUM) Explicit periodic ab-initio (DFT) calculations are a widely established tool for the study of extended system such as surfaces or bulk crystals. Yet, on top of the high computational costs they often suffer from severe shortcomings for both charged systems, such as intermediates in photo-electrocatalysis, and the description of solvation effects. For the former, periodic calculations result in energy offsets due to finite size effects necessitating additional corrections and large supercells. The explicit description of Solvation effects, on the other hand, demands a sampling over solvent degrees of freedom, which are most of the time irrelevant to the problem at hand. In my talk I will outline how embedding of fuly quantum mechanical regions into coarse-grained classical environments for both solids and liquids can provide at least approximative remedy for these shortcomings. I will roughly outline the theoretical underpinnings of the methods involved and give examples of their use for state of the art research.