This article highlights how dislocation dynamics (DD) simulations provide a unique opportunity for establishing scale transitions in crystal plasticity. Recent progress in this numerical method is briefly reviewed. Based on the standard problem of plasticity in fcc crystals, we show that DD simulation insight provides guidelines for modeling material mechanical properties controlled by the collective behavior of dislocation microstructures. Hence, DD simulation allows more physical input to be incorporated into continuum models for strain hardening, thereby improving their predictive ability.