About 100 cells divide every second in our body. A key protein in cell division is a protein kinase termed Plk1, because it activates other proteins involved in this process. Plk1 is also overexpressed in many types of cancer. This makes it a promising target for cancer therapies. However, drugs that inhibit Plk1 have often proven ineffective. New findings by researchers led by Peter Lenart and Monica Gobran may help to improve therapeutic approaches. They discovered a previously unknown function of Plk1: It regulates the timely onset of cell division. When the protein is inhibited, cells start dividing many hours later.