Computer simulations and animations of the motion of atoms as a chemical reaction proceeds give a detailed picture of how the reaction occurs at a microscopic level. This information is particularly useful for testing the accuracy of statistical models, which are used to calculate various attributes of chemical reactions. Such simulations and animations, in concert with experimental and ab initio studies, have begun to provide a microscopic picture of the intimate details of a particular class of gas-phase ion-molecule bimolecular reactions known as SN2 nucleophilic substitution. In these reactions, a nucleophile is displaced from a molecule by another nucleophile. The dynamical model of SN2 reactions that emerges from the computer studies, and its relation to statistical theories, is discussed here.