Theory, modeling and simulation (TMS) have been repeatedly identified as key enabling technologies for making fundamental advances in nanoscience and for making nanotechnology a practical reality. In this talk, we provide an overview of the role of TMS in nanoscience, as well as an introduction to our ongoing theoretical and simulation-based research programs in applications such as nanotribology, nanoscale complexity of the electric double layer, molecular electronics, hybrid organic-inorganic nanocomposites and nanoconfined fluids.