Despite the success of quantum chromodynamics (QCD) in describing many aspects of the strong nuclear force, several critical aspects of this interaction are not well understood. Chief among these is how the fundamental degrees of freedom in QCD, quarks and gluons, are manifest in hadronic collisions at very high energies, and whether the density of low momentum gluons becomes saturated. Answering this question requires new experimental data and is a major element of a proposed electron-ion collider facility (EIC). Ultra-peripheral heavy-ion collisions (UPCs) provide an alternative means to address this question. In highenergy ion beams like those at the LHC or RHIC, the intense electromagnetic fields of the nuclei serve as sources of high-energy quasi-real photons, leading to photon-nucleus reactions. Like in deep inelastic scattering, the photon serves as a well understood probe that can be used to investigate the structure of the target. While the potential of UPCs was identified long ago, many measurements have only recently become experimentally accessible, leading to rapid developments in the field. This talk will present the current status of UPC measurements, their relationship to foundational issues in QCD and their synergy with the physics program of future EIC facility.