Figure reports the transition matrices of the two model systems with the strongest self-assembling drive, namely the Ms at ε = 50 kJ mol -1 and the BTAs at T = 300 K. We note that the molecules/fragments are exchanged between the various size assemblies in a similar way in both systems. In these conditions, the monomers (when they do not remain disassembled) tend to flow toward the most stable aggregates in the systems (33 -64 and 65 -128-mers). At larger sizes, this is again contrasted by the fiber tendency to fragmentation. Analogous similarities hold also for the cases of M with ε = 45 or ε = 40 kJ mol -1 and BTA at T = 320 or T = 340 K respectively (see Figure , and Figure in the SI).