This chapter describes experimental techniques that are used to characterize multilayer systems. The goal is to provide some background information on the relevant experimental methods. There is discussion on the Surface Magneto-Optic Kerr Effect (SMOKE). Linearly polarized light can change its polarization (and be-come elliptically polarized) upon reflection from a magnetic surface (or in the presence of a magnetic field). Depending on the direction of magnetization, different forms of polarizations of the reflected beam can occur. There are 3 Kerr configurations that are of significance. They are: polar, longitudinal, and transverse. An important advantage in SMOKE appears to be associated with the fact that a relatively simple, in situ analysis of the polarized beam can be carried out external to the UHV chamber where the sample is located. It has become the technique of choice for basic characterization of magnetic films. Significant insights into changes in the magnetic states have been obtained from in situ SMOKE experiments conducted on thin films. The Kerr rotation is associated with some intricate details of the electronic/magnetic structure, so its magnitude is a complex function of the wavelength of the incident light used. The chapter discusses auger electron spectroscopy (AES), ferromagnetic resonance (FMR), scanning tunneling microscopy (STM), Atomic Force Microscopy (AFM), Neutron diffraction, Mössbauer spectroscopy, Low Energy Electron Diffraction (LEED), reflection high energy electron diffraction (RHEED), angle resolved photo-emission spectroscopy (ARPES), x-ray absorption spectroscopy (XAS), Magnetic Dichroism in XAS, x-ray photoelectron emission microscopy (X-PEEM), spin polarized low energy electron microscopy (SPLEEM), and Andreev reflection. The oscillatory behavior of the X-ray absorption coefficient carries information about the local environment of a given atom in the solid state. Even in transition metal atoms, when core levels are probed, relativistic effects can play an important role. This is exactly the case when core levels are probed by X-rays.