For many years, experiments and computer modeling methods have been significantly used for characterizing the microstructures of mesoscopic materials in order to study their relationship to desired properties and in order to optimize the materials design and performance. In fact, many problems related to the properties of materials, such as cor￾rosion, fatigue crack formation, fracture, mechanical responses, piezoelectric responses, and etc, are three-dimensional in nature because most practical mesoscopic materials have a polycrystalline or multi-phase structure with significant complexity in the spatial arrangement of the microstructural units (for example, spatial and size distributions of grains and particles, grain boundary and interphase boundary character/energy distri￾butions, orientation texture, and etc.). This is especially true for metallic and ceramic structural and functional materials, since they are subject to various processes (for example, rolling, extrusion, tempering, sintering and etc) before commercializing. Therefore, it is of great interest to charac￾terize microstructural parameters and to reveal their effects on the properties of the materials in three dimensions for studying microstructure-property relation￾ships.