Scientists have developed a DNA sensor in living cells that allows real-time monitoring of DNA damage and repair. This sensor is based on a natural protein that binds to damaged DNA for a short time, faithfully displaying the repair process without the need to freeze the cells. This allows scientists to observe the spread of damage, the arrival of repair proteins at the site of damage and the actual moment of DNA repair. This approach provides a detailed view of the cellular emergency response and the dynamics of the repair mechanisms. Such a sensor enables a better understanding of DNA repair mechanisms directly in living cells, which is important for cell biology research and potentially for medicine. The results represent a new tool to study DNA damage and repair in the natural environment of the cell.