Molecular modeling is playing an increasing role in materials and life sciences. The "multi-scale simulations for materials and life sciences" symposium will review recent method developments and their applications ranging from small building blocks to large supramolecular assemblies, biomacromolecules and nanomaterials. It will cover reactivity aspects in these systems, as well as theoretical characterizations of their many optical, electronic, and magnetic properties. After a brief general introduction, we illustrate in this paper some aspects of the research in this broad field by giving examples of our recent achievements within the three main topics tackled during the symposium, i.e. the simulation of nonlinear optical properties of molecules and molecular aggregates, the charge and energy transfer properties in materials, as well as quantum chemical simulations in biological media.