The shear-induced crystallization behavior of isotactic polypropylene (i-PP) has been investigated by in situ optical microscope under various thermal and shear histories. A shish-kebab structure during growth was observed under a well controlled, however, weak shear field. According to our results under these weak shear and thermal history, a modified model was proposed for the growing process of melt shear-induced crystallization of i-PP. Furthermore, many physical insights were provided on several still unsettled issues such as extended chain crystals, row nuclei, and smectic ordering questions. (c) 2005 Elsevier Ltd. All rights reserved.