The article discusses the importance of standardizing immunophenotyping assays, particularly flow cytometry, for the Human Immunology Project. Flow cytometry is a powerful tool for analyzing cellular phenotype and function in the immune system, allowing for the characterization of various cell subsets, including rare ones, in complex mixtures like blood. However, the variability in reagents, sample handling, instrument setup, and data analysis hinders the reliability of results. The authors outline the current state of standardization in flow cytometry and propose steps to enable the Human Immunology Project. These steps include defining standardized antibody cocktails, optimizing sample handling, standardizing instrument setup, and improving data analysis methods. They also highlight the need for centralized data collection and mining to facilitate the comparison of results across studies and laboratories. The article emphasizes that while flow cytometry is primarily used in research settings, there is growing interest in standardizing human immunophenotyping to achieve the goals of the Human Immunology Project.The article discusses the importance of standardizing immunophenotyping assays, particularly flow cytometry, for the Human Immunology Project. Flow cytometry is a powerful tool for analyzing cellular phenotype and function in the immune system, allowing for the characterization of various cell subsets, including rare ones, in complex mixtures like blood. However, the variability in reagents, sample handling, instrument setup, and data analysis hinders the reliability of results. The authors outline the current state of standardization in flow cytometry and propose steps to enable the Human Immunology Project. These steps include defining standardized antibody cocktails, optimizing sample handling, standardizing instrument setup, and improving data analysis methods. They also highlight the need for centralized data collection and mining to facilitate the comparison of results across studies and laboratories. The article emphasizes that while flow cytometry is primarily used in research settings, there is growing interest in standardizing human immunophenotyping to achieve the goals of the Human Immunology Project.