If measured from beginning to end, the DNA in our cells is too long to fit into the cell’s nucleus, explaining why it must be constantly folded and packaged. When it is time for cell division, and the genetic information needs to be passed on to the next generation, DNA must be packed particularly tightly, else serious consequences for a cell’s viability might ensue. In a trans-European team effort, researchers from the Max Planck Institute of Molecular Physiology in Dortmund (MPI), the Netherlands Cancer Institute, and the Human Technopole in Milan have now discovered a molecular switch that regulates DNA packing into the typical sausage-shaped chromosomes observed during cell division. The discovery of this central mechanism for cell division has many potential applications in medicine and biotechnology.