Quantitative information on the internal dynamics of the NP can be obtained by tracking the SOAP spectra of all atoms at each sampled MD snapshot and monitoring their change. In particular, this allows us to analyze to what SOAP AE each atom belongs to at time t and at each successive timestep (i.e., at t + dt, with dt = 1 ns in our analyses). Figure shows a normalized transition matrix for the Ih 309 NP at 300 K. This contains all probabilities (all values reported in the matrix are to be intended as multiplied by ×10 -2 ) for an atom in a given AE i to remain in that AE (p ii ) or to undergo transition to a different AE (p i→ j ) in dt (the rows of the matrix sum to 1). Note that while such normalized transition matrices are non-symmetric (due to normalization), the corresponding raw matrices counting all transitions between the AEs observed along the MD are substantially symmetric (Supplementary Figure ), as it pertains to a microscopic equilibrium along the sampled MD regime (Supplementary Figure ). Figure shows that at 300 K the deep/core AEs tend to be rather stable (p ii ∼ 1: atoms belonging to such AEs have a high probability of remaining in such state in dt = 1 ns). On the other hand, a significant inter-AE exchange is already observable (p i→ j ≥ 1) at this temperature on the NP surface. Indeed, the matrix shows that in such conditions most of the action takes place in the sub-square in the matrix connecting the 'Faces', 'Edges', and 'Vertexes' AEs (dark-, light-green, and yellow AEs).