Single-crystalline beta-Ni(OH)(2) nanoplates of hexagonal structure have been synthesized through a hydrothermal process. The beta-Ni(OH)(2) nanoplates possess well-defined hexagonal shapes with landscape dimension of 45-140 nm and thickness of 20-50 nm. The in-plane surfaces of hexagonal-shaped nanoplates lies on (0 0 1), and the side surfaces are (10 0), (0 (1) over bar0) and (1) over bar 10). Post-thermal decomposition of the beta-Ni(OH)(2) nanoplates led to the formation of single-crystalline NiO nanostructures with landscape dimension of 25-120 nm including nanorolls, nanotroughs and nanoplates. The sizes of the central hole in NiO nanorolls and the low-lying ground in NiO nanotroughs are in the range of 10-24 nm. The optical absorption bands in the wavelength range of 350-800 nm have been interpreted according to the ligand field theory. (C) 2008 Elsevier B.V. All rights reserved.