There is a wide range of early developmental assessment or screening instruments. Standardized, reliable assessment instruments (e.g., Mullen Scales of Early Learning, Brigance Inventory of Early Development, Battelle Developmental Inventory, etc.) allow for direct evaluation of infant/child behaviors but they are time intensive, expensive to purchase, require highly trained personnel for administration, scoring, and interpreting, and often rely on outdated norms. The purpose of the NIH Infant and Toddler Toolbox (aka the “NIH Baby Toolbox” [NBT]) is to develop and nationally norm an easy to administer, score, and interpret infant and toddler assessment inventory of cognition, social functioning, language (receptive and expressive), numeracy, self-regulation, executive function, and motor function for research and clinical use in children between 1- to 42-months of age that will include direct child assessment (preferred measurement), supplemented as needed by parental/ legal guardian report. To complete the NIH Toolbox, Northwestern will extend its relationship with Sage Bionetworks, a Seattle-based nonprofit research and development organization specializing in Apple and Android data collection. Northwestern researchers will also coordinate measurement development efforts by researchers at the University of Denver, Florida State University, University of Minnesota, Johns Hopkins University, and New York University.