Research with the Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab) has revealed new insights into short-range correlations—the brief pairings of nucleons (protons with neutrons, protons with protons, or neutrons with neutrons) in the nuclei of atoms. The study, published in Nature, used precision measurements to determine that short-range correlations differ depending on the density of the nucleus, that is, how many nucleons it contains.