This book details recent advances in all aspects related to scale transition in crystal plasticity and damage, with a particular focus on the challenges associated with the characterization and modeling of this class of complex interactions. The following topics are included: Innovative characterization techniques (multi-scale characterization, SEMTEM coupling, TEM-micro-diffraction coupling, in-situ mechanical tests, localization, image correlation, displacement field measurements, tomography, etc.). Computational crystal plasticity and damage (dislocation dynamics and ab initio calculations, microstructure evolution of polycrystals, comparison between FE, fast Fourier transform and self-consistent approaches, intragranular slip, heterogeneities, discrete approaches, etc.). The book gathers together selected papers from the invited lectures presented at the 3rd and 4th US-France Symposia organized by the editors under the auspices of the International Center for Applied Computational Mechanics (ICACM).