Light microscopy enables biosensors to be used to characterize the cellular environment (pH, ROS, calcium, etc.) in order to highlight differences between populations or identify heterogeneities within tissues or cells themselves. Cytometry allows multiparametric analyzes offering the possibility of measuring several activities simultaneously cell by cell. It is thus easy to compare the results obtained, to deduce their interdependence or not, which makes it an essential tool for the study of cell signaling.