We review our recent experiments by linear optical spectroscopy in the visible spectral range on interface controlled monolayers and thin films of π-conjugated organic molecules on well-defined surfaces. In particular, cw fluorescence and fluorescence excitation spectroscopy are considered. We discuss two interesting aspects: the possibility to prepare interface controlled films with non-bulk like structures, and consequently different and possibly superior optical properties, and the use of optical spectroscopy as an analytical tool to investigate properties of interfacial organic films.