As partially anticipated, the establishment of ground state Pt•••Pt metallophilic interactions causes a dramatic change in the photophysical properties of the assemblies destabilizing the HOMO resulting in a bathochromic shift of both absorption and emission spectra (41). This peculiar characteristic of such class of compounds renders the assembled structures better light harvesters compared to the monomeric unit, enabling the fibers to absorb light up to approximately 550 nm, while the monomer complex 1 cannot absorb light with λ > 450 nm, and complex 2 exhibits the most hypsochromic shift with absorption bands only in the UV region with an absorption onset at 400 nm (Fig. ). This provides a basis for the photoselective elongation (Fig. ): by mixing assembled fibers with a fresh solution of complex 2 and irradiating at λ = 555 nm, where only the supramolecular fibers absorb light (Fig. ), the reduction of complex 2 can occur solely through photoinduced electron transfer (PET). In this setup, the aggregated form would synthesize its own monomer 1, promoting the growth of the assembly rather than forming new nuclei, as monomer 1 would be generated only in the immediate vicinity of the existing fibers. To a solution of 2 (1 mL, 10 -3 M in ACN/H2O 2:1) were added a 20 μL of a dispersion of aggregates obtained by photoreduction (same solvent and concentration), then, 20 μL of the This elongation kinetics can be explained by the fact that Pt(II) forms on the surface of the fibers. As the fibers increase in size, the conversion of Pt(IV) to Pt(II) also increases, leading to faster elongation. While the establishment of Pt•••Pt metallophilic interactions and the geometric change from Pt(IV) to Pt(II) are crucial for this study, these concepts could be extended to redoxactive organic molecules with aggregation-induced emission (AIE) or those capable of forming 20 H-or J-aggregates. This advancement paves the way for precision macromolecular engineering and the development of life-like materials.