The electron density at the BCP of each hydrogen bond is marked on the figure. From the IGMH map, it is clear that H-bonds 2 to 5 are stronger than H-bonds 1 and 6, as the centers of the isosurfaces of the former are blue, while those of the latter are completely green. However, it is difficult to distinguish which of H-bonds 2 to 5 is stronger simply by visualizing the color of the isosurfaces. Since the electron density at the BCP has been shown to correlate positively with hydrogen bond interaction energy, the order of H-bond strength can be accurately determined as 25>34>16 based on the marked electron density at the BCPs. This example demonstrates that combining visual analysis methods such as IGMH with the quantitative analysis in the QTAIM framework can be highly beneficial.