The article discusses the development and application of 17-color flow cytometry, a sophisticated technology used to analyze complex cellular populations. The authors highlight the advantages of using multiple colors in flow cytometry, such as improved accuracy and sensitivity in detecting rare cell populations. They describe the instrumentation, including the use of three diode-pumped solid-state lasers (blue, green, and violet) and a red helium-neon laser, and the detection system, which consists of photomultiplier tubes and optical filters. The article also covers the challenges in developing reagent panels, such as selecting appropriate antibodies and fluorochromes, and the importance of viability markers and controls like FMO (fluorescence-minus-one) controls for accurate data interpretation. Additionally, it discusses advanced data analysis techniques, including automated cluster analysis and bivariate gating, and the need for user-friendly software to handle complex data sets. The authors conclude by emphasizing the potential of 17-color flow cytometry in immunology and clinical research, particularly in identifying correlates of immune protection and disease outcomes.The article discusses the development and application of 17-color flow cytometry, a sophisticated technology used to analyze complex cellular populations. The authors highlight the advantages of using multiple colors in flow cytometry, such as improved accuracy and sensitivity in detecting rare cell populations. They describe the instrumentation, including the use of three diode-pumped solid-state lasers (blue, green, and violet) and a red helium-neon laser, and the detection system, which consists of photomultiplier tubes and optical filters. The article also covers the challenges in developing reagent panels, such as selecting appropriate antibodies and fluorochromes, and the importance of viability markers and controls like FMO (fluorescence-minus-one) controls for accurate data interpretation. Additionally, it discusses advanced data analysis techniques, including automated cluster analysis and bivariate gating, and the need for user-friendly software to handle complex data sets. The authors conclude by emphasizing the potential of 17-color flow cytometry in immunology and clinical research, particularly in identifying correlates of immune protection and disease outcomes.