What do the fast dynamics tell us about aggregation?

Two typical morphology of two-dimensional aggregates are considered: compact crystalline clusters and string-like non-compact conformations. Simulated trajectories of both types of aggregates are analysed with fine spatial resolution. While the long-time geometry of such trajectories appears to be statistically identical for two conformations, the self-overlap statistics reveal two distinct short-time {\em pre-caging} mechanisms. While the time-scale is directly proportional with length-scale for particles in a compact aggregates, an inverse relationship holds for non-compact clusters. These short length-fast time relationship of particle localization might hold the key to the structure-function relationship of aggregate forming systems and other non-equilibrium soft materials.