T cells expressing chimeric antigen receptors (CARs) have shown exciting promise in cancer therapy， particularly in the treatment of B-cell malignancies. However， optimization of CAR-T cell production remains a trial-and-error exercise due to a lack of phenotypic benchmarks that are clearly predictive of anti-tumor functionality. A close examination of the dynamic changes experienced by CAR-T cells upon stimulation can improve understanding of CAR-T-cell biology and identify potential points for optimization in the production of highly functional T cells.