In Science this week, a group led by Georg-August University Gottingen researchers report on new details about how long strands of DNA stay tightly bundled in replicating cells. Previous studies have shown that chromosomes' ability to condense during metaphase is related to activity at the tails of histones. The new findings show that during early mitosis, phosphorylation of a major histone protein recruits the chromosome passenger complex, which helps regulate the process. This leads to interactions between various histone proteins that cause chromosomes to tighten up during metaphase.