Single crystals of K2V3O8 have been synthesized using a mild hydrothermal method. The synthetic method allows morphological micro-patterning of well aligned tubular-windows on sheet-like K2V3O8 single crystals. The lateral dimensions of the tubular-windows range from 2 to 0.1 mum and are ca. 80 mum in depth. (C) 2004 Elsevier B.V. All rights reserved.