Studies of reaction kinetics at the single enzyme level have become possible due to the swift development of single molecule detection techniques. In this tutorial review, which targets both general and expert research chemists in the biochemical or physical (organic) chemistry field, we briefly introduce some of these fluorescence microscopic techniques and discuss selected studies on single molecule enzymology. The nature of the frequently observed fluctuations in the reaction rate, the so-called dynamic disorder, is described based on various available models.