Condensins are key players in mitotic chromosome condensation. Using an elegant combination of state-of-the-art imaging techniques, Walther et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201801048) counted the number of Condensins, examined their behaviors on human mitotic chromosomes, and integrated the quantitative data to propose a new mechanistic model for chromosome condensation.