While high energy physics discovers more and more fundamental particles, it leaves behind an ever growing complex world that requires a different mathematical representation: This is the essence of Chemistry as pointed out by Carl Anderson. In contrast to featureless point masses in Mechanics, a molecule in Chemistry has a large number of internal degrees of freedom in terms of atoms, electrons, etc. The behavior of even a single biomolecule, a protein in an aqueous environment, is often so complex that the mathematical representation of biochemical kinetics has to be statistical. In this talk, I present a classical, stochastic description of general chemical reaction systems in solution and show how J. W. Gibbs' macroscopic equilibrium chemical thermodynamics can be derived as a mathematical result, with an entropic force as its center piece. Our theory is actually applicable to mesoscopic open chemical systems such as a single living cell. I then discuss the application of this theory to understand the notion of non-genetic phenotype switching, in terms of a landscape, in cell differentiation and cancer heterogeneity.