ZnO nanowires were grown from an aqueous solution at low temperature (95 degrees C) on Corning glass and silicon (100) substrates. It turns out that the deposition of a thin ZnO seed layer on the substrates prior to the chemical growth is crucial for obtaining c-axis oriented ZnO nanowires with controllable dimensions. The nanowires' diameter increases with the grain size of the ZnO seed layer. On the other hand, aqueous solution growth on bare substrates leads to the formation of flowerlike nanostructures, consisting of nanorods, with no preferred growth orientation. The dimensions and morphology of these complex nanostructures depend mainly on growth time. Furthermore, the complex ZnO nanostructures do not show high transmittance, while the nanowires are highly transparent in the visible part of the spectrum. (C) 2009 Elsevier B.V. All rights reserved.