Microstructure reconstruction in 3D and quantitative digital representation are enabling consideration of polycrystalline and multi-phase microstructures in mechanics codes in a realistic way. To take full advantage of these advances, we discuss in this chapter the synergy of coupling quantitative microstructure characterization by experimental imaging techniques with quantitative microstructural evolution modeling by image-based computer simulation techniques such as the phase field method. Specific attention will be paid to the fundamentals of the phase field method for microstructure representation and description of microstructure evolution, and procedures of using experimental images as model inputs. Through individual examples we show how to use the phase field method at different length scales to: explore mechanisms of microstructural evolution, extract important materials parameters, carry out physics-based repairs of experimentally reconstructed microstructures, and evolve existing microstructures or generate new microstructures to populate digital microstructural database for different time, temperature, stress, and other service conditions for mechanical property explorations.