Publisher Summary When transition metal oxides are supported on and chemically interact with the surface of the typical oxide carriers—such as Al2O3 and TiO2—they form well-dispersed monolayers in the form of two-dimensional compounds, unlike those found at the surface of the unsupported oxide. This chapter characterizes the dispersion state of the well-dispersed monolayer ferric oxides on various supports (γ-Al2O3, TiO2, ZrO2, and MgO) by XANES and EXAFS. The modifications of the interaction on the reaction performance of these supported systems have also been studied by three model reactions. The curve fitting results of EXAES data, as well as the features of the XANES, indicate that the dispersion state of Fe3+ changes from one support to another. The very low CN of next neighboring Fe3+ with a relative long distance verifies that the Fe3+ is basically dispersed in monolayers. The modification of the interaction on the reaction performance is not the same for the different reactions.