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 1 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.