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Fabrication of uniform two-dimensional (2D) structures from small molecules remains a formidable challenge for living self-assembly despite its great success in producing uniform one-dimensional (1D) structures. Here, we report the construction of unprecedented uniform 2D platelets with tailorable shapes and controlled sizes by creating new nuclei from a donor-acceptor (D-A) molecule and 1-hexanol to initiate 2D living self-assembly. We demonstrate that the D-A molecule undergoes 1-hexanol-induced twisting to form continuous alternative hydrogen bonds in-between under electrostatic attraction, which in turn forms a new nucleus. This connection architecture of the new nucleus allows to simultaneously regulate the growth rate of in two dimensions to generate 2D platelets of distinct shapes through simply varying the amount of 1-hexanol relative to hexane. Furthermore, the living nature of the new nucleus enables seeded growth of complex concentric multiblock 2D heteroplatelets by sequential and alternative addition of different D-A molecules. Interestingly, the resulting 2D platelets obtained by such living self-assembly exhibit enhanced photostability compared to those obtained by conventional self-assembly without the involvement of 1-hexanol.