Cell and nucleus size vary dramatically between developmental stages, cell types and species. During metazoan early development, embryos do not increase in volume, and cell divisions result in smaller cells. Mitotic spindle length, centrosome size and nuclear size are known to scale with cell size. A study in Caenorhabditis elegans now reveals that cell size and nuclear size regulate chromosome length independently. High-resolution imaging of intact embryos showed that cell size reduction beyond a certain threshold was accompanied by chromosome shortening. Uncoupling nuclear and cell sizes by disrupting the RAN·GTP gradient across the nuclear membrane showed that chromosomes can become shorter in response to reduced nuclear size independently of cell size. The exact mechanisms that regulate chromosome compaction to attain specific lengths remain to be elucidated.