SUMMARY The main mission of the P41 Biomedical Technology Research Resource for Macromolecular Modeling and Bioinformatics (P41-GM104601) over the last three decades has been developing state of the art computational technologies for biomolecular and cell simulations and visualization, implementing them in efficient, economical, user-friendly software solutions, and disseminating them to the biomedical community at no cost. The Resource has enabled high-quality, rigorous research for the biomedical scientists who need to integrate molecular and cell modeling, simulation, and visualization in their research, not only at diverse academic institutions, but also in industry. The flagship software programs, VMD and NAMD and their auxiliary plugins, are used currently by more than 125,000 users and have received a staggering number of 57,000 citations (19,711 in 2018-2021 alone), reflecting the massive use of the technologies and programs developed by the Resource, and its sub- stantial economies of scale. The Resource's partnership with the biomedical community resulted in the 2020 ACM Gordon Bell Special Prize for COVID-19 Research. Under the R24 mode of operation, a major goal of the Resource will be to ensure that its software solutions remain current and available to its large user base on existing and upcoming hardware platforms commonly used at local and institutional levels, and at national super- computing centers, where a large fraction of the overall time is consumed by biomedical researchers using the Resource's programs. Given the key position of these programs, several major supercomputing centers as well as major hardware vendors have established strong relationships with the Resource, even directly supporting software development and optimization. In addition, the Resource will ensure the utility of its programs by includ- ing algorithmic changes/updates that are critical to applicability of the codes and/or demanded by the community. The Resource will also sustain and expand its comprehensive user training program, empowered by an already existing, large collection of online tutorials, case studies, and hands-on workshops. Another major activity of the Resource will be to continue to support its users in the proper and efficient application of the software programs through customer support services and expanding and upgrading the documentation for the programs. The R24 Resource for Macromolecular Modeling and Visualization will be evaluated on a continuous basis by monitoring quantitative metrics such as the number of its active users (users of multiple versions of software) and citations, by conducting regular user surveys requesting input from the user community which will also assist in identifying most critical features and improvements, and by the technical input from the external advisory board.

NARRATIVE Computer-based modeling, simulation, and visualization of molecular systems have evolved as indispensable tools for modern science and medicine. Over the past three decades, the NIH Resource at Illinois has provided some of the most advanced and widely used (currently with more than 125,000 users) software packages that make computational tools and algorithms for molecular and cell modeling readily and freely available to the biomedical community. Beyond developing computational technology driven by the needs of its very large user base, the Resource is engaged in training activities supported by an unparalleled number of fully online and heavily used set of tutorials, case studies, workshops, and a heavily visited web site.