A variety of industries – information technology, aerospace, automobile, and basic and new materials manufacturing – need technological innovations, which bring high-value-added and high-quality products at low cost not only because of global competition, but also because of the perspective of en- ronmental consciousness and regulation. Thermophysical properties of hi- temperature melts are indispensable for numerical simulations of material processes such as semiconductor and optical crystal growth of the melt, and castingofsuper-high-temperaturealloysforjet-engineturbineblades,inad- tion to welding in automobile manufacturing. Recent developments in process modeling provide 3D unsteady analysis of melt convection, temperature, and heat ?ux distribution, which enables us to predict product quality. In fact, 3D process visualization using computer modeling helps us to understand complicated phenomena occurring in the melt and to control the process. Accurate data are necessary to improve the modeling, which co- e?ectively engenders high-quality products. However, crucial obstacles render measurements of thermophysical properties di?cult at elevated temperatures because of high chemical reactivity and ?uidity of melts. Substantial and persistent challenges have been made to ascertain the precise thermophysical properties of high-temperature melts. This book describes the new techniques and latest developments in the measurements of atomic structure, density, surface tension, viscosity, heat capacity, thermal and mass di?usivity, th- mal conductivity, emissivity, and electrical conductivity of high-temperature melts. In addition to up-to-date improvements in conventional techniques, some new attempts are introduced to open a new scienti?c ?eld, that is,physics of high-temperature melts.