Using a noncontact atomic force microscope, we found that single molecules in a chiral helical pi-conjugated polymer could form a unique periodic structure having a pitch of about 20 nm on the surface of a mica substrate. The diversity of the periodic structures is also discussed. Some basic insights into the characteristics of single molecules (or their individual characteristics) in pi-conjugated polymers are revealed. (C) 2004 Wiley Periodicals, Inc.