In the present work, we reported a novel method for the synthesis of well-dispersed flower-like ZnO microstructures derived from highly regulated, well-dispersed ZnO nanorods by using low temperature (100 degrees C) hydrothermal process and without using any additional surfactant, organic solvents or catalytic agent. The phase and structural analysis were carried out by X-ray diffraction (XRD) which confirms the high crystal quality of ZnO with hexagonal (wurtzite-type) crystal structure. The morphological and structural analyses were carried out by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which indicate the formation of well-dispersed ZnO nanorods as well as flower-like ZnO. It has been shown that flower-like ZnO is made up of dozen of ZnO nanorods building block units. The high resolution transmission electron microscopy (HRTEM) and their corresponding selected area electron diffraction (SAED) pattern show that both ZnO nanorods and flower-like ZnO microstructures are single crystalline in nature and preferentially grow along [0001] direction. Their optical property was characterized by photoluminescence spectroscopy: shows ZnO nanorods have only violet emission and no other emission while Flower-like ZnO microstructures have a weak violet emission and a strong visible emission. A plausible growth mechanism of ZnO nanorods as well as flower-like ZnO microstructures has been given. (C) 2010 Elsevier B.V. All rights reserved.