Multiscale materials modeling has grown to become a defined area of materials research with its own history. Six biennial forums of the MMM series held so far have served to overview the current and steer the future developments in materials simulations towards more realistic and therefore more complex materials models and computational algorithms. Given that much of the observed complexity emerges at various microstructural length scales, it appears important for the MMM community to further focus on advancing our understanding of and capabilities for modeling material microstructure and its evolution. With this important need in mind, we define the overall theme for MMM 2014 to be "The Microstructural Frontier". In reference to the pioneering spirit of the American West, we would like to focus attention of the MMM community on the inadequacy of exiting capabilities for quantitative modeling of materials microstructural evolution and on the wide open and still unexplored horizons for developing the needed capabilities in the future.