Book excerpt: Nanocrystalline materials are three-dimensional ultrafine, polycrystalline microstructures. They give rise to interesting and useful chemical and physical-size effects. This book describes the development of a method of synthesizing chemical vapor for the production of nanocrystalline ceramic powders. The development of the microstructure during sintering is studied and the influence of the synthesis parameters on the structure and properties of the nanocrystalline ceramics from the atomic to the microstructural level is investigated. The emerging unified view, from powder synthesis and ceramic processing to structural characterization and determination of properties, provides a detailed understanding of the materials and enables better quality control of the end products.