This paper illustrates, with several examples, the spectral resolution and attainable sensitivity reached with sub-Doppler laser spectroscopy in cold argon beams, seeded with molecular or metal vapors. Linear as well as nonlinear spectroscopy has been applied. The detection techniques use either LIF or resonant two-photon ionization. Examples given include NO2, SO2 and Na3-molecules. The advantage of optical double resonance methods is illustrated.