The properties of semiconductive nanocrystals deviate from those of their bulk counterparts, the structure loses translational symmetry and quantum confinement effects result in an increased bandgap as the size approaches that of a large molecule (Fig. ) . Quantum dots (QDs) are exploited for optoelectronics and quantum informatics among other applications , and are sometimes regarded as "artificial atoms" for their bound and discrete electronic states . Ideally, they are to be made with high quantum yield and sufficient size uniformity for any applications, and with precise shape control for mimicking valency and bond directionality to be used as material voxels or artificial nanocrystal molecules . However, this stringent requirement has been more difficult to meet as the QDs become smaller , previous literature being unable to synthesize small, high quality, deep-blue emitting perovskite quantum dots with reasonable purity . This is because their synthesis has been modelled after colloid synthesis relying on hot injection methods under nitrogen : high temperatures promote rapid nucleation growth kinetics making the synthesis harder to control the smaller the materials become. In addition, the conventional metrics of purity assessment such as photoluminescence quantum yield (PLQY) and full width at half maximum (FWHM) are unsuitable for atomic precision analysis of individual QD particles. Inspired by recent advances in self-organization chemistry , and analysis by transmission electron microscopy (TEM) with millisecond and angstrom spatiotemporal resolution , we set two goals in this study: atomic precision synthesis via templated growth of magic-sized perovskite nanoclusters and atomistic analysis using the single-molecule atomic-resolution time-resolved electron microscopic (SMART-EM) imaging . We demonstrate that, in a ligand-less synthesis, perovskite precursors quickly grow to form elongated dodecahedra and cuboids (Fig. ). By adding Malic Acid (MLA) we could prevent the formation of irregular structures and instead formed micron-sized cubes, whose size could be decreased by addition of oleylamine, leading to the exclusive formation of ≈ 2.5 nm blue emitting perovskite nanoclusters. ≈ m (Fig. )