Although known since antiquity, mechanochemistry has remained dormant for centuries. Nowadays, mechanochemistry is a flourishing research field at the simultaneous stages of gathering data and (often astonishing) observations, and scientific argumentation toward their analysis, for which the combination of interdisciplinary expertise is necessary. Mechanochemistry’s implementation as a synthetic method is constantly increasing, although it remains far from being fully exploited, or understood on the basis of fundamental principles. This review starts by describing many remarkable advantages of mechanochemical reactions, simplifying and “greening” chemistry in solutions. This description is followed by an overview of the current main weaknesses to be addressed in the near future toward the systematic study of its energetics and chemical mechanisms. This review finishes by describing recent breakthrough experimental advances, such as in situ kinetics monitoring using synchrotron X-ray powder diffraction and Raman spectroscopy, plus equally significant computational chemistry approaches, such as quantum mechanochemistry, used for the understanding of covalent or hydrogen bond ruptures in biomolecules or mechanophores in polymers at the single-molecule level. Combined with new technologies to control temperature and pressure in ball mills, these appealing new methods are promising tools for establishing the fundamental knowledge necessary for the understanding of mechanochemical reactivity and mechanisms.