Solution-processed organic–inorganic hybrid perovskites have attracted attention as light-harvesting materials for solar cells and photonic applications. The present study focusses on cubic single crystal; microstructures of CH3NH3PbBr3 perovskite fabricated by a one-step solution based self-assembly method. It is seen that, in addition to the nucleation from the precursor solution, the crystallization occurs when the solution was supersaturated, followed by formation of small nucleus of CH3NH3PbBr3 that will self-assembled into bigger hollow cubes. A 3D fluorescence microscope investigation of hollow cubes confirmed the formation of hollow plates on the bottom, then the growth starts from the perimeter and propagate to the center of the cube. Furthermore, the growth in the (001) direction follows a layer-by-layer growth model to form a complete cube, confirmed by SEM observations. To get more insights into the structural and optical properties, density functional theory (DFT) simulations were conducted. The density of state (DOS) calculations revealed that the valence band maximum (VBM) consists of states contributed by Br and Pb, which agrees with the X-ray photoelectron spectroscopy valence band (XPSVB) measurements.