Using a chemistry-based analogy for stellar dynamics, I will address the question: What is missing from modern simulations of star cluster evolution? The basic idea is simple: More massive clusters have larger velocity dispersions and are hence dynamically hot. This leads to the rapid ionization or disruption of most multiple star systems during direct dynamical encounters, in analogy with the collisional destruction of molecules and/or atomic ionization in a hot gas. Low-mass clusters such as open clusters, on the other hand, are dynamically cold. Here, stars and multiples are able to more effectively “stick together” during encounters, much like atoms forming molecules in a cold gas. The longer-lived dynamical interactions stimulate a more complicated dynamical environment, produce richer multiple star populations, and generate a number of complicating effects not properly accounted for by simulations.