At low concentrations and low excess Zn : HmIm molar ratio (excess molar ratio refers to any ratio higher than stoichiometric 1:2 ratio), Classical Nucleation Theory (CNT) can be considered to hold; the material nucleates via the formation of crystal nuclei. In line with the above-discussed ideas, small, crystalline, and well-faceted ZIF-8 particles (with a radius of gyration of R g ∼ 20 nm, equivalent to a 50 nm diameter sphere) were reported during the first ∼ 300 s of synthesis, which were called Crystalline Primary Particles by Cravillon et al.