As a case study of colloidal superlattice composed of large AAs held together by smaller and mobile EAs, here we focus on the recently reported colloidal supercrystals of positively charged TMA-NPs coassembled with negatively charged, trivalent CIT ions (Figure ). At the experimental level, TMA-NPs can be coassembled with CIT ions in water to produce well-defined, compact superlattices, in which the TMA-NPs (AAs) are arranged into an FCC lattice (Figure ). All-atom and consistent implicit-solvent coarse-grained (CG) models (Figure ) showed how the large population of -3e charged CIT ions allows stabilizing the assembly of two TMA-NPs, overcoming the electrostatic repulsion between the positively charged TMA-NPs. Noteworthy, even while stabilizing the NP-NP interaction, the CIT ions were observed to preserve a dynamic behavior (Figure ). In such a two-NP model, unsupervised clustering analysis of Smooth Overlap of Atomic Positions (SOAP) -highdimensional descriptors effective in classifying the ionic environments surrounding each CIT molecule along the MD simulation based on their level of order/disorder -detected three main CIT environments: CIT ions at the NP-NP interface (Figure : blue), CIT ions interacting with a single NP (red), and an intermediate ionic layer (green). In general, the interface (blue) CIT ions are more static and the red ones are more dynamic, while the ionic environments are in dynamic communication in equilibrium condition via a continuous exchange of CIT ions. The interconnection plot of Figure (right), identifying the dynamic CIT transitions between the various environments, shows the allowed transitions in the system. Such a rich dynamic behavior of the CIT ions fits well with the experiments, allowing the initially formed amorphous aggregates to rearrange into ordered FCC crystalline lattices (within hours). At the same time, the TMA-NP-CIT superlattice offers an ideal system that can be studied as a supercrystal of AAs surrounded and held together by mobile EAs.