A three-dimensional (3131) lamellar structure of a poly(styrene-block-isoprene) block copolymer was observed at submicrometer and micrometer levels by scanning electron microscopy combined with a focused ion beam (FIB-SEM). The 3D lamellar structure with an exceptionally large periodicity, about 0.1 mu m, was successfully reconstructed, and the size of the reconstructed image by FIB-SEM was 6.0 x 6.0 x 4.0 mu m(3), which was greater than the transmission electron microtomography data, 3.8 x 3.9 x 0.24 mu m(3), by a factor of about 40. This result indicates that 3D reconstruction using FIB-SEM is quite useful for direct 3D observations, especially analyses of polymeric materials at the submicrometer and micrometer levels. (c) 2007 Wiley Periodicals, Inc.