The NIH Toolbox is the result of an ambitious project supported by the National Institutes of Health to develop a comprehensive, standardized, and highly accessible test battery to be used in research. Dr. Julie Hook is the Product Manager for the project and is in large part responsible for the development of the Toolkit. Rolf and Joe discuss with Julie a wide ranging set of topics related to the science of cognitive, sensory, and motor testing, including some of the core design principles and theortical considerations.