Our cover features images related to flow cytometry techniques widely used for analysis of function and phenotypes of major human and murine immune cell subsets, superimposed on a multidimensional immune cell population scatter plot. These images are taken from the third edition of Flow Cytometry Guidelines (Cossarizza et al. pp. 2708–3145), a comprehensive resource prepared by flow cytometry and immunology research experts from around the world. The Flow Cytometry Guidelines not only highlight the latest trends and best practices of flow cytometry used in basic and clinical laboratory use, but also re-enforce optimal data analysis, enabling the correct use of state of the art flow cytometry.