In vivo, cellular responses are initiated, organized, and regulated by individual cells exerting various functionalities. The cells present in varying frequencies and degrees of activity ultimately determine these elaborate processes and their outcome. Indeed, most responses show extensive cellular heterogeneity, especially when immune cells are involved in infection, immunization, autoimmunity, or neoplastic disease. Even within seemingly homogeneous subpopulations, intrinsic heterogeneities in the cell cycle, history, metabolism, activity, and stochastic gene expression modify the cellular functionality. Ultimately, functional plasticity further complicates the study object and can lead to various outcomes and trajectories of these responses in individuals. Therefore, the state and evolution of cellular functionality of individual cells ultimately determine the response and its outcome.

Our vision aims to advance the analysis of individual cellular functionalities quantitatively. We focus on developing and applying novel analytical strategies that allow for the direct, quantitative, and deep-​​phenotypic analysis of cellular functions with single-​​cell resolution. Going beyond pure development, we aim to measure, understand and exploit the function of individual cells within a complex cellular response and tissue. In our vision, individual cells are the functional mediators and organizers of cellular responses, and the study of cellular functionality provides the means to decipher and understand complex cellular responses.