Researchers at Utrecht University have created a groundbreaking fluorescent DNA sensor that allows scientists to observe the entire timeline of DNA damage and repair within living cells. This state-of-the-art technology enables real-time imaging, offering unprecedented clarity into how cells respond to genetic injury and restore their DNA integrity. Unlike traditional methods, which typically involve freezing cells at various stages and yield only static snapshots, this new sensor provides a dynamic view of cellular processes. The sensor is crafted from a natural protein that gently and temporarily binds to damaged DNA. This transient interaction allows the sensor to mark areas of damage without disrupting the cell's natural repair mechanisms. The study, published in Nature Communications, highlights the sensor's potential applications in vital fields, including cancer biology, drug safety assessments, and aging research. By enabling continuous monitoring, the fluorescent sensor dramatically improves scientists' ability to observe and analyze the moment DNA damage occurs, track the rapid arrival of repair proteins to the damaged site, and witness the restoration of DNA. This continuous observation replaces the outdated practice of conducting numerous experiments to capture different moments in cellular response. The ability to see the entire repair timeline in one cohesive view enables better understanding of the mechanisms behind DNA repair, which is crucial for advancing cancer treatments and drug development. Cancer therapies often involve inducing DNA damage in tumor cells, making precise measurements of DNA damage inflicted by compounds a critical aspect of early-stage drug assessment. Although this sensor does not serve as a treatment itself, it could revolutionize medical research by providing deeper insights into cellular responses and enhancing the development of effective therapies.