GENERAL OVERVIEW: The Flow Cytometry Core at NEI provides flow cytometry analytical and sorting equipment and services to the NEI Intramural community. It utilizes and develops state-of-the-art sample preparation, data acquisition and analysis, and sorting procedures in collaborative research projects. Provides training to students, fellows, and principal investigators on sample preparation, staining, and post-sort handling. Assesses technical research needs and recommends recruitment of the appropriate staff and acquisition of the equipment needed to meet those needs. The core also supports NIH intramural research outside NEI by processing samples for laboratories without access to flow cytometry instrumentation and collaborations with the Foundation for Advanced Education in the Sciences. The instrumentation of in the core is aging. This is the last year that the FACSAria II will have an option for a maintenance contract. There is newer instrumentation that is interesting to the NEI Intramural Research Program. The COVID19 crisis still affects the operation of the core. The future of the core is also pending the direction of the incoming Scientific Director for the NEI IRP. SERVICES PROVIDED BY THE CORE: This year, fifty-fivindividuals from twentyfour different laboratories used the facility. These services and collaborative services were performed for Principal Investigators (PIs) from 4 NEI organizations (NNRL, LI, DIR, OGVFB), plus other NIH investigators outside NEI. This year the core performed 500 hours of sorting and over 10,000 samples were analyzed. Among the techniques now in use within the core are methods for phenotyping live cells, gene expression detection through fluorescent reporter genes, monitoring membrane and DNA content changes due to apoptosis or proliferation, measurement of intracellular proteins and quantification of soluble proteins. The work involving human tissues includes the sorting of peripheral blood mononuclear cells to study their cytokine production, genotype and DNA or RNA expression. The sources are blood, buffy coat, and white cells. Some analytical work had been done with eye fluids, eye tissue specimen, protein, and tears. The National Eye Institute made a great investment in biosafety with the addition BD FACSAria Fusion flow cytometer equipped with a fully integrated biosafety cabinet. This sorter meets the recent NIH's operator and sample protection requirements as well as global standards for bioprotection for processing human samples. No human tissues were stored by the core. The Core encourages, but does not require, users to acknowledge the Core contribution in their publications. TRAINING: Several formal training sessions were offered by the Core to the NEI community. These courses included: Introduction to Flow Cytometry, Advanced Techniques (Ex. Apoptosis applications), Analytical Instrument Operation and Data Analysis with FloJo Software. The Core stuff received about 100 hrs. or training a year in flow cytometry. The Core stuff provided about 50 hrs of training to the NEI community and 60 hrs of training through FAES to the NIH community.