Silver is a well-known catalyst for partial epoxidation of ethylene and selective oxidation of methanol to formaldehyde. It is too complicate in real catalyst system to understand and manipulate. The size, structure of the silver clusters and the oxygen species are closely related to the reactivity and selectivity. Recent results illustrate that not only the clusters but also the interaction between clusters and supports played an important role in the activation of a catalytic process, as the A...