Nucleate

Nucleate is a verb meaning to form a nucleus around which a new phase or structure develops. In scientific usage, nucleation is the initial step in processes such as crystallization, condensation, or bubble formation, marking the transition from a metastable state to a more stable phase. The term derives from nucleus, the central core that seeds growth.

Nucleation occurs when fluctuations or impurities create a stable cluster that can grow. A nucleus must reach a critical size to overcome the energetic cost of creating new interfaces. Nucleation can be homogeneous, occurring uniformly within a supersaturated or supercooled medium, or heterogeneous, occurring on surfaces, impurities, or interfaces that lower the energy barrier.

In materials science, nucleation controls crystal size and microstructure during solidification or precipitation hardening. In atmospheric science, condensation and ice nucleation on aerosols determine cloud properties and behavior. In solutions, nucleation can drive crystallization, either spontaneously or as seeded growth, to separate solutes.

In biology, the term is often used in the context of nucleated cells, meaning cells that contain a nucleus. Most animal, plant, and fungal cells are nucleated, while some blood cells in mammals are anucleate.

Nucleation theory links microscopic fluctuations to macroscopic phase changes. Classical nucleation theory and its extensions describe how factors such as temperature, supersaturation, interfacial energy, and impurities influence the rate at which a new phase forms.