The atomic arrangement and grain growth of the hexagonal structured Ge2Sb2Te5 were investigated by a transmission electron microscopy study. Unlike the isotropic crystallization of face-centered-cubic (fcc) structured Ge2Sb2Te5, the hexagonal structured Ge2Sb2Te5 grain was preferably grown to a large degree with a specific direction. As a result, we have revealed that the grain growth occurred parallel to the (0001) plane, and identified the atomic arrangement of the hexagonal structured Ge2Sb2Te5 having nine cyclic layers by analyzing the high-resolution transmission electron microscopy images and simulated images obtained in the direction of < 1120 > zone axis. (c) 2006 Elsevier B.V. All rights reserved.