In this study, we used cross- sectional transmission electron microscopy to directly visualize the internal structure of regioregular poly( 3- hexylthiophene) ( P3HT) on hydrophobized insulator substrates. By examining the variation in the electron contrasts, we found that these P3HT films are self- organized with layered molecular ordering. Further, by analyzing grazing incidence- angle X- ray diffraction results, we found that highly oriented, nanoscopic domains composed of P3HT chains with face- on orientations are present.