nucleation* [@cohen; @tuomas_review] and *two-stage nucleation*. [@knowles_two_stage] Further work shows that the kinetics of self-assembly is strongly dependent on which of the above mentioned pathways are active in the assembly process. [@curve_fitting] The influence molecular aggregation pathways have on the early time kinetics of linear self-assembly, which is the most studied aspect of the problem in hand, motivates researchers to study and characterize all possible pathways. [@tuomas_science; @cohen; @knowles_two_stage; @Tiwari_2016; @tuomas_review]

With the aim to probe the molecular pathway responsible for linear self-assembly in the context of supramolecular polymerisation, Albertazzi *et al.* recently performed experiments with a self-assembling molecule known as 1,3,5 benzenetricarboxamide or BTA for short. [@albertazzi] By imaging the supramolecular polymers at different assembly times, they were able to investigate monomer mixing on the scale of individual polymers. Because their observations could not be explained by any of the hitherto known molecular pathways, they suggested the need to revisit theoretically and experimentally the dynamic behaviour of supramolecular polymers. From their observations, they conclude that the molecular pathway responsible for self-assembly of BTAs is the one in which the monomer can be removed from and inserted anywhere along the polymer backbone.

We have schematically depicted the novel pathway in 