During an adaptive immune response, lymphocytes proliferate for five to 20 generations, differentiating to take on effector functions, before cessation and cell death become dominant. Recent experimental methodologies enable direct observation of individual lymphocytes and the times at which they adopt fates. Data from these experiments reveal diversity in fate selection, heterogeneity and involved correlation structures in times to fate, as well as considerable familial correlations. Despite the significant complexity, these data are consistent with the simple hypothesis that each cell possesses autonomous processes, subject to temporal competition, leading to each fate. This article addresses the evidence for this hypothesis, its hallmarks, and, should it be an appropriate description of a cell system, its ramifications for manipulation.