A simple method for the fabrication of self-aligned nanogaps and fluidic nanochannels by using conventional photolithography combined with patterned-size reduction technique is presented. The method is based on the complete conversion of a photolithographically microstructured metal layer - exhibiting a high expansion coefficient -to a metal oxide with an improved pattern size resolution using thermal oxidation. With this technique, there are no principal limitations to fabricate nanostructures with different layouts down to several nanometer dimensions. In this work, the proposed method is experimentally demonstrated by preparing self-aligned nanogaps and nanochannels on a Si-SiO2 substrate down to 15-20 nm dimensions. (C) 2009 Elsevier Ltd. All rights reserved.