 The abstract summarizes the research conducted by the authors, who discovered that interstitial atoms in face-centered cubic, FCC, metals form compact 3D inclusions of a 15-franc-casper phase before forming dislocation loops. These inclusions act as sources of prismatic or faulted dislocations depending on the energy landscape of the host material. The authors used cutting-edge atomistic simulations to demonstrate this scenario in aluminium, copper, and nickel. Their findings suggest that the fundamental mechanisms of interstitial defect formation are more complex than previously thought and require a general revision. This article was authored by Alexandra M. Goreva, Christoph Domain, Alain Chartier, and others.