Abstract: Compared to their crystalline form, amorphous drugs exhibit higher solubility and faster dissolution rate and thus enhancing oral bioavailability of poorly water soluble drugs. However, since the amorphous form is thermodynamically unstable relative to the crystalline form, amorphous solids tend to crystallize over time and subsequently negate their advantages. This review briefly describes fundamental aspects of amorphous substances and highlights the recent advances of fast crystallization behaviors. Understanding the inherent crystallization mechanisms of amorphous materials is of utmost importance in order to control the physical stability and lead to efficient formulation development of amorphous pharmaceutical solids.