In a recent study, Purvis and colleagues (Chao et al, 2019) quantify cell cycle phase durations in human cells and propose a model whereby cell cycle progression in single cells is a succession of uncoupled, memoryless phases, each composed of a characteristic rate and number of steps. They also suggest that having such memoryless phases is a feature of healthy cells, while cancer cells have correlated phases. Silvia Santos (Crick, London) and Lendert have written a News&Views piece about this article.