The purpose of this Brain Research through Advancing Innovative Neurotechnologies (BRAIN) Initiative is to encourage applications that will develop and validate novel tools to facilitate the detailed analysis of complex circuits and provide insights into cellular interactions that underlie brain function. The new tools and technologies should confer a high degree of cell-type and/or circuit-level specificity. Validation of the utility of the tool/technology is an essential feature. A particular emphasis for this funding opportunity announcement (FOA) is the development of new genetic and non-genetic tools for delivering genes, proteins and chemicals to cells of interest; new approaches are also expected to target specific cell types and or circuits in the nervous system with greater precision and sensitivity than currently established methods. Tools developed through this initiative that can be used in a number of species/model organisms rather than those restricted to a single species are highly desired. Applications that provide approaches that break through existing technical barriers to substantially improve current capabilities are also encouraged.