If we were to ask the reader to pick a single observable to characterize the nucleation process, the so-called crystal nucleation rate J would probably turn out to be a very popular choice. J is a scalar quantity that represents the average probability, per unit time and per unit volume, for a critical crystalline nucleus to occur within the supercooled liquid or the supersaturated solution of interest. The apparently straightforward nature of J makes it ideal to compare the crystallization kinetics of the same system in different conditions or indeed between different systems as well. Crucially, J can be both measured experimentally and estimated by means of computer simulations, thus providing, in principle, a much sought after connection between reality and modeling. However, long-standing major inconsistencies between experiments and simulations still persist as of today, despite the ever-growing capabilities of molecular simulations.3,4