T cells are extremely diverse with regard to their phenotype, function, anatomic localization and migratory behavior, even when they harbor exactly the same T cell receptor. As a consequence, not all T cell subsets play an equal role in for example the control of infections and tumors, or the pathology associated with inflammatory disorders. Using a combination of several state-of-the-art single-cell technologies, we study how different CD8 T cell subsets arise, and what mechanisms underlie their specific properties.