Polycrystalline materials behave as elastic, relatively rigid bodies under small loads, but exhibit plastic deformation and flow under sufficiently large applied stresses.  Despite the practical importance of such plasticity, its scientific understanding is still poor.  This is due to its inherent complexity, involving as it does the nonequilibrium behavior of ~10²⁴ atoms, which exhibit a host of different phenomena on the various relevant scales.  In recent years, a multiscale approach to the theoretical modeling, numerical simulation, and experimental study of these phenomena has been pursued.  In this talk, a brief survey of the simulation methods used will be presented, including Density Functional Theory (Angstrom and nanometer scales), Molecular Dynamics (tens and hundreds of nanometers), Dislocation Dynamics (microns), and Finite Element Crystal Plasticity (tens and hundreds of microns).  A critical reassesment of the multiscale program will be given, emphasizing the need to develop theoretical insight and to diversify the set of simulation tools used.  Time permitting, an attempt at such development, involving pattern formation on a micron scale, will be discussed.