This is a recurring workshop devoted to multi-scale atomistic simulation methods for condensed phase studies, with some emphasis on those involving (but not limited to) Density Functional Tight Binding and machine learning approaches. Multi-scale simulations can generally span a wide range of energies, from covalent and metallic bonding to dispersion interactions, and can involve reactive events and/or electronically excited states. To help maximize state-of-the-art developments, we plan to bring together leading developers and practitioners of these methods in order to identify current grand challenges for condensed phase problems as well as appropriate benchmarks for novel approaches. Our hope is that the workshop will foster collaborations that help tackle these challenges and lead to the next generation of multi-scale, QM-based methods that are applicable to a broad range of chemical, materials, and biological problems.