Nickel base single crystals are among the major materials achievements of the twentieth century. Among all structural materials, nickel-base alloys are unique for their ability to operate at 90% of their melting point with substantial mechanical loads in chemically severe environments. Design advances in these materials have been synonymous with advances in the performance and efficiency in aircraft and power-generation turbines, rocket engines, and nuclear power plants. Our research focuses on the design of new alloys that are compatible with advanced thermal barrier coating systems, development of new single crystal solidification processes that can produce physically large single crystals for power generation systems, development of rejuvenation approaches to extend the lifetimes of these high value materials and for predicting their behavior during processing and in service environments.