Disorder plays a fundamental role in many natural and man-made systems that are of industrial and scienti?c importance. Of all the disordered systems, hete- geneous materials are perhaps the most heavily utilized in all aspects of our daily lives, and hence have been studied for a long time. With the advent of new - perimental techniques, it is now possible to study the morphology of disordered materials and gain a much deeper understanding of their properties. Novel te- niqueshavealsoallowedustodesignmaterialsofmorphologieswiththeproperties that are suitable for intended applications. With the development of a class of powerful theoretical methods, we now have the ability for interpreting the experimental data and predicting many properties of disordered materials at many length scales. Included in this class are ren- malization group theory, various versions of effective-medium approximation, percolation theory, variational principles that lead to rigorous bounds to the - fective properties, and Green function formulations and perturbation expansions. Thetheoreticaldevelopmentshavebeenaccompaniedbyatremendousincreasein the computational power and the emergence of massively parallel computational strategies. Hence, we are now able to model many materials at molecular scales and predict many of their properties based on ?rst-principle computations.