110th Anniversary: Mesoscale Complexity—To Dodge or To Confront?

This commentary briefly addresses the complexity at mesoscales of different levels, describes the limitations of traditional approaches, and introduces the preliminary principle of the potential mesoscience. It is believed that mesoscale complexity arises from collective effects, and emerges within mesoregimes. Such complexity makes the averaging approaches (based on the assumption of homogeneity) solely at the system scale (or within each computational grid) problematic while the ab initio approaches solely at the element scale are commonly unaffordable to achieving system behavior. The difficulty in finding a single-objective extremal principle and the invalidity of the homogeneity assumption indicates that the equilibrium framework might not be a good starting point to understand the behavior of systems far from equilibrium. Focusing on the specific degrees of freedom at mesoscales and revealing the corresponding multiple dominant mechanisms seemingly pave a promising way, and this methodology leads to the concept of mesoscience. Some topics closely related to chemistry have been proposed within such a framework as well.