From the knowledge of thermodynamics, it is known that if a system is in equilibrium, the Gibbs free energy of the system is minimal, and the equilibrium phase in the system is called the stable phase, if the system is in a metastable state, the phase at this time is called the metastable phase. The system has a tendency to transition from a non-equilibrium state to an equilibrium state, so the metastable phase also has a tendency to transition to the stable phase.