Cell size set by cell cycle regulation In the Arabidopsis meristem, cell sizes are regularized despite asymmetric cell divisions. D'Ario et al. describe a balanced regulatory system that controls the duration of the growth phase of the cell cycle preceding DNA synthesis. KIP-related protein 4 (KRP4) inhibits progression to DNA synthesis. Because the amount of KRP4, which binds to mitotic chromosomes, is titrated to the amount of chromosomal DNA, daughter cells begin with similar amounts of KRP4 despite possible asymmetric cell divisions. Deviations are adjusted as excess KRP4 is degraded and the cell size is normalized. Science , abb4348, this issue p. 1176