Low energy electron microscopy (LEEM) is used to study the quantum size effect (QSE) in electron reflectivity from thin films. Strong QSE interference peaks are seen below 20 eV for Cu and Ag films on the W(1 1 0) surface and Sb films on the Mo(0 0 1) surface. Simple inspection of QSE interference peaks reveals that all three metals grow atomic layer-by-atomic layer. Layer-specific I(V) spectra obtained with LEEM permit structural analysis by full dynamical multiple scattering LEED calculations for a layer-by-layer view of thin film structure.