“…Theoretical predictions tend to deviate significantly from experimental results in orders of magnitude in nucleation and reaction rates of the crystalline particles. − Different experimental studies and approaches demonstrated empirically multiple possible formation pathways toward the final crystal through the inclusion of prenucleation clusters, liquid droplets, gels, primary amorphous or crystalline nanoparticles, nanoaggregates, or mesocrystals . In the past two decades, a large variety of these transitional precursor phases of crystalline substances were discovered in pharmaceuticals, , proteins, − organic molecules, , thin films, , biominerals, , and inorganic materials. ,,− …”