Models based on an average cell are useful, but they may not accurately describe how individual cells really work. New possibilities opened up with the advent of single-cell live imaging technologies. Now it is possible to peer into the lives of individual cells. In a new paper in PLOS Genetics, a team of biologists and physicists from Washington University in St. Louis and Purdue University used actual single-cell data to create an updated framework for understanding the relationship between cell growth, DNA replication and division in a bacterial system.