Fluorescence polarization is a powerful technique for characterizing energy transfer (ET), internal packing, and chromophore orientation in supramolecular assemblies in solution, as well as in the solid phase. When combined with fluorescence microscopy imaging (referred to as fluorescence polarization imaging), it can be used to visualize and characterize energy transfer dynamics in such anisotropic assemblies. The anisotropy in our light-harvesting and. The more pronounced blue emission was observed for the nanofibers oriented along the vertical (north/south) direction in Figure , which became green emitting fibers in Figure . The color contrast was partially reversed between the north/south (vertical) and east/west (horizontal) oriented nanofibers (Figure ), with more greenish emission in in Figure (I||) and more blueish emission in Figure (I┴), suggesting a strong dependence of the polarized emission on the orientation of the nanofibers growth axis. As discussed earlier, red spots appear at some nanofiber junctions, and no significant change in emission color was observed when the emission polarization direction was changed from perpendicular to parallel to the excitation beam, indicating a rather random orientation of (S)-2PDI