This notice of funding opportunity (NOFO) seeks applications to develop theories, models and methods (TMM) as tools that will advance a quantitative and predictive understanding of brain function across multiple scales, including behavior. Priority will be given to projects that develop novel capabilities for analyzing, integrating, and interpreting the large-scale, complex data emerging from the Brain Research through Advancing Innovative Neurotechnologies® (BRAIN) Initiative and related efforts, which includes cell-type specific physiological, anatomical, connectivity, and behavioral data. Proposed experimental work must be limited to model parameter estimation and/or testing the validity of the tools being delivered. It is expected that the TMM tools developed under this NOFO will be made widely available to the neuroscience research community for their use and modification.