The most fundamental nuclear fusion in nature, the synthesis of the neutron from the hydrogen atom in the core of stars, is a physical process of extreme importance, as it literally allows the stars to "turn on". This synthesis cannot be described by quantum mechanics, due to its impossibility to describe the "excess mass" in the neutron, bigger than the sum of the masses of the proton and of the electron, as well as for other technical insufficiencies, and this is an important confirmation of the EPR argument on the lack of completeness of quantum mechanics. For this reason, Santilli proposed in April 1978 the "completion" of quantum mechanics into an axiom-preserving but non-unitary form which he called hadronic mechanics [1].  In this lecture, we outline Santilli's achievement via hadronic mechanics of a numerically exact representation of "all" characteristics of the neutron in its synthesis from the hydrogen at the non-relativistic and relativistic levels [2], subsequent systematic experiments on the laboratory synthesis of the neutron from the hydrogen conducted by Santilli and a number of collaborators including the author [3], and the importance of this synthesis for basic advances on controlled nuclear fusions.