When, in 1935, the famous ‘EPR’ article – so called from the initials of its authors – was published, the scientific community had to face not only the manifest challenges that the argument meant to show, but also some hidden problems that would later arise. The incompleteness of quantum mechanics, which the EPR article aimed to prove, was indeed grounded on a very problematic principle, the locality principle, later challenged by the experiment first thought by Bohm and then performed by Aspect. The aim of this article is to delineate the development of the problem of nonlocality, from its origins to the proof of its existence in the quantum worlds, where, as Bell showed, the hidden variables cannot do anything in order to dispel nonlocali...