Femtoscopy, historically associated with Hanbury-Brown–Twiss (HBT) interferometry, has evolved into a precision tool for investigating the space-time structure of particle-emitting sources created in high-energy collisions. While the term HBT is often used, it captures only a subset of the broader class of femtoscopic correlation techniques based on quantum-statistical correlations. This review provides a systematic overview of femtoscopic measurements across a broad range of collision energies and system sizes. We explore the “sizes” of homogeneity regions through detailed energy scans, spanning from the low-energy regime of HADES to the highest energies of the RHIC Beam Energy Scan and the LHC. We examine the system-size dependence of these regions, including the intermediate regime of \ (p\) –Pb collisions at the LHC, which serves as a bridge between elementary \ (p\) –\ (p\) and dense \ (A\) –\ (A\) systems, while highlighting the breakdown of universal multiplicity scaling due to initial-state geometric effects. Furthermore, we discuss non-identical particle correlations, such as \ (\) –\ (K\), as a unique probe of relative space-time emission asymmetries, providing independent evidence for collective transverse expansion. The review also addresses “interaction femtoscopy” exploiting the sensitivity of correlation functions to final-state interactions in order to extract scattering parameters for (anti) protons, \ (\) hyperons, and light nuclei. These measurements impose important constraints on hyperon–nucleon and three-body interactions, supplying essential input for chiral effective field theory and the equation of state of dense nuclear matter, with significant implications for the internal structure of neutron stars. Abstract Published by the Jagiellonian University 2026 authors
H. Zbroszczyk (Thu,) studied this question.