The microstructure of Cu(In,Ga)Se2 (CIGS) films with compositions ranging from Cu-rich to In-rich was investigated by transmission electron microscopy (TEM) and energy-dispersive Xray spectroscopy (EDS). We found that the Cu-rich samples have larger grain sizes than the Inrich sample. In the Cu-rich samples, sub-interfaces were observed. The two sides of the subinterfaces were found to have different Cu concentration. In the In-rich sample, Ga inhomogeneity across grains was observed.