The process of initiation of a new phase in a cryogenic (liquid) or supersaturated (for solution or steam) environment; the initiation of a phase change of a substance to a lower thermodynamic energy mode (steam to liquid condensation, steam for fast deposition, liquid to freeze). in the wild, heterogeneous Nucleation is the more common, where such a change takes place on small particles of different composition and structure. Homogeneous Nucleation occurs when the change of the State centers on embryos that are found in the same initial state as changing fabric. in this case the Nucleation system contains only one component, and the so-called homogeneous Nucleation. in meteorology, especially in Cloud physics, a number of types of Nucleation is of interest. The process by which the Cloud condensation nuclei embarks on phase change from steam to liquid is important in all Cloud formation problems. Physical nature of the freezing nuclei that may be responsible for the conversion of supercooled water drops to ice crystals is critically important in precipitation theory, which is the clarification of homogeneous Nucleation near − 40 ° c. role of thermodynamics, all Nucleation processes involve free energy decrease associated with bulk phase change and free energy increase is associated with the creation of new interfaces between phases.