The morphology of the PNPls were further evaluated by the form factor modeling from SAXS data measured in two sample-to-detector distances: 3.8 and 0.3 m. A parallelepiped form factor included in Irina macros for IgorPro ® software was used for the modeling of the PNPls. For more details on data reduction and modeling form factor, see Methods section. To perform the analysis, we used parameters from the STEM images and the absorption spectra to provide an initial guess of the size parameters (A = thickness, B and C = lateral dimensions with A < B < C). For instance, for Br-170, which is the sample with the most regular size distribution among the ones investigated here, we chose the mean thickness to be 1.77 nm (n = 3) with a standard deviation of 0.33 (the variation of a single octahedron layerunitary scale). We also chose the largest size of the nanoplate (C) to be about 11 nm (estimated from the distance between the columns -Figure ). The model adjusts well to the data, and the resulting fit is shown in Figure (light gray curve). The parameters from the fit are summarized in Table and, for sample Br-170, the fitting parameters agree with the ones from the STEM images. For sample Br-110, we started with a thickness of 2 layers (1.18 nm) and much larger length for C. Although the model fits the scattering data well (Figure ), the correlation between SAXS and STEM results (Table and) is not direct. Apparently, the size measured from the STEM images is not the thickness of the NWs, but its B-side (Table ). Evidence for that is the low contrast presented by the NWs in the transmission mode of electron microscopy (Figure ), suggesting that they are lying flat on the plane of the TEM grid. The thickness found from SAXS modeling, although slightly overestimated, is in closer agreement with n = 2 NWs presenting the optical properties from Figure .