We present a tutorial review of our quantum state resolved experiments designed to study gas–surface reaction dynamics. The combination of a molecular beam, state specific reactant preparation by infrared laser pumping, and ultrahigh vacuum surface analysis techniques make it possible to study chemical reac- tivity at the gas–surface interface in unprecedented detail. We describe the experimental techniques used for state specific reactant preparation and for detection of surface bound reaction products developed in our laboratory. Using the example of the reaction of methane on Ni and Pt surfaces, we show how state resolved experiments uncovered clear evidence for vibrational mode specificity and bond selectivity, as well as steric effects in chemisorption reactions. The state resolved experimental data provides valuable benchmarks for comparison with theoretical models for gas–surface reactivity aiding in the development of a detailed microscopic understanding of chemical reactivity at the gas–surface interface.