Wide-and Small-Angle X-ray Scattering (WAXS and SAXS): X-ray scattering experiments were carried out in a Xenocs Xeuss 2.0 equipment in two sample-to-detector distances: 0.3 and 3.8 m. The X-ray source was a GeniX 3D with a copper target with photon energy of ~8 keV (λ = 1.5419 Å). The detectors used were a Dectris Pilatus 300 k for SAXS and Dectris Pilatus 100 k for WAXS (WAXS detector was at 36 ° with respect to the X-ray beam). The colloidal suspensions of the perovskite nanoplates (with several concentrations) were loaded in 1.5-mm borosilicate capillaries, as well as their dry samples. To prepare the dry samples, we filled the capillaries with 80 mg/mL hexane suspensions, placed them inside a desiccator with the help of a rack, and dried the solvent under reduced pressure for at least an hour. All the measurements were performed in ambient atmosphere with controlled temperature and humidity. The background for the samples was collected using their neat solvent in a capillary. The integration time for each acquisition was 300 s. The calibration of the distances for the 2D scattering curves was performed using silver behenate as a standard. We calibrated and reduced the data (radial integration of the 2D scattering image to obtain a scattering curve) using the Nika 62 macros for IgorPro ® software. To obtain the scattering curves from Figure (I(q) vs q), we merged the curves from the two sample-to-detector distances and subtracted the respective backgrounds. To model the scattering curves, we used a parallelepiped form factor included in Irina 41 package for IgorPro software. Details of the parallelepiped function can be found in the sasview documentation. 63 UV-visible absorption spectroscopy: Absorption spectroscopy was performed in a Carry 60 UV-Vis Agilent Technologies spectrophotometer, using a 10-mm quartz cuvette. All the spectra were collected using ~0.2 mg/mL hexane suspensions of the perovskite nanoplates. A neat cuvette with neat hexane was used as a background.