The present developments in the physics of complex systems, in particular, the struc- tural relaxation of supercooled liquids and glasses, are discussed by using a stochastic cluster- based model. We are able to depict the impact of the interface between the nucleus considered as a cluster of a certain number of molecules and the liquid phase for the enhancement of the overall nucleation process. It is also shown that even a relatively simple stochastic model, which appears phenomenological if it is not agent-based, can describe precisely the outcomes from multiple agent-based simulation runs where probabilistic insight is lacking and which should be long enough to equilibrate the states of large systems.