The equilibrium dynamics of supramolecular systems involves a continuous exchange of molecular entities. Relevant questions concerning such communication between assemblies are: do all fibres exchange the same kind of fragments? Or do they To study in detail what species are exchanged among the fibres at the equilibrium, we monitored the assembly (size) to which each monomer belongs to at each step, and tracked their transitions every ∆τ time interval. We analysed in this way the CG-MD trajectories at equilibrium (t CG = 20 -40 µs) with a sampling time interval of ∆τ = 300 ps, frequent enough to reduce the probability of assemblies undergoing multiple binding/unbinding events during ∆τ (see Methods for details). We thus obtained transition matrices (Figure , centre) counting how many times a monomer is exchanged from an assembly of size i (matrix row index) to another of size j (column index). Normalizing the matrix rows to 1, we obtain transition probability matrices: the numbers on the diagonal are indicative of the probability that a monomer inside an assembly of size i remains in that assembly during a ∆τ interval. The off-diagonal entries are indicative of the probability that a monomer in an assembly of size i is involved in a transition, becoming part of a larger (i-to-j, where j > i) or smaller ( j < i) assembly during ∆τ (Figure , left and right).