The participating NIH Institutes and Centers invite Research Project Grant (R01) applications to develop assays for high throughput screening (HTS) for use in Probe and Pre-therapeutic Discovery. Through this FOA, NIH wishes to stimulate research in 1) developing assays for specific biological targets and disease mechanisms relevant to the mission of participating NIH Institutes with the intent to screen for small molecule compounds that show potential as probes for use in advancing knowledge about the known targets, identifying new targets, or as pre-therapeutic leads; and 2) establishing collaboration with screening centers that have the requisite expertise and experience needed in implementation of HTS assays for the discovery and development of small molecule chemical probes. This FOA seeks to establish a stream of scientifically and technologically outstanding assays for screening by the NIH Molecular Libraries Production Centers Network (MLPCN) in the Molecular Libraries Program (MLP) and other academic centers. One important criterion for this initiative is novelty, so applicants are therefore encouraged to avoid focusing on areas and approaches that have been extensively targeted in other settings. Assays should be relevant to the scope of research in at least one of the participating NIH Institutes.