👉 In chemistry, a nucleation is an event in which a solid substance (the substrate) spontaneously forms into a liquid or gas when exposed to sufficient heat and/or pressure. This process can occur in various conditions such as solidification, melting, sublimation, condensation, evaporation, or precipitation. Nucleations are often the first step in the chemical reactions that form the structure of molecules, which is crucial for the subsequent stages of biological, chemical, and physical processes. Nucleations