Chemical master equation, i.e., a birth-death process with continuous time, has become the mathematical foundation of chemical reaction kinetics in both small and large systems. It has wide applications to biochemical models in cellular biology. In this talk, I shall discuss the unifying theory that encompasses both stochastic models and deterministic nonlinear chemical oscillations. The essential difference between open and closed system s in terms of the "chemical detailed balance" will be discussed. The dynamic consequences of open-systems will be presented.