Electron confinement or quantum well (QW) state manifests in metallic thin films as the film thickness is reduced to nanometer scale. Photoemission provides the most direct observation of QW states in k-space. The unique capabilities now available at the Advanced Light Source (ALS) at Berkeley make it possible to image QW states on the atomic scale. The photoemission results from ALS on Cu thin films grown on fcc Co(100) are presented using single- and double-wedge samples. First, we will discuss how the QW states are formed in the Cu film and how to describe it using the phase accumulation model. Second, we will show how the QW states result in the oscillatory interlayer coupling between two ferromagnetic Co layers across a thin Cu layer.