The investigation of multi-component complex systems composed of oxides, nitrides, and carbides has intensified in the last few years. reviews some of the recent advances inthe understanding of these composite systems, providing insight into how phase diagrams can be utilized in the fabrication of whiskers and ceramic-matrix whisker-reinforced ceramics. Phase relations and sintering information is reviewed for transparent polycrystalline oxides. Phase diagrams are discussed to predict alkali oxide corrosion of alumino-silicate references.