Researchers from the Perelman School of Medicine at the University of Pennsylvania have invented a new way to map specific DNA markings called 5-methylcytosine (5mC) which regulate gene expression and have key roles in health and disease. The innovative technique allows for scientists to profile DNA using very small samples and without damaging the sample which means it can potentially be used in liquid biopsies (testing for cancer markers in the bloodstream) and early cancer detection.