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Physicists using the ALICE experiment at CERN's Large Hadron Collider measured particle production at unprecedented spatial resolution, revealing nuclear structures as small as roughly a quarter the size of a proton. The results showed a surprising drop in J/ψ production at the smallest scales that conventional 'nuclear shadowing' theories struggle to explain, offering a new way to distinguish between competing models of gluon behavior deep inside atomic nuclei. The findings could refine fundamental understanding of the strong nuclear force and the structure of matter at subatomic scales.