Polyaniline nanofibres can be prepared by a number of methods based on chemical oxidative polymerization(1-7) and in situ adsorption polymerization(4-6). However, the lack of alignment in these nanostructures makes them unsuitable for many applications. Here, we report a simple approach to chemical oxidative polymerization that can control the growth and simultaneous alignment of polyaniline nanofibres grown on a range of conducting and non-conducting substrates in a wide variety of sizes. The diameters of the tips of the nanofibres can be controlled within the range 10-40 nm, and the average length can be controlled within the range 70-360 nm. Moreover, the coatings display a range of properties including superhydrophilicity and superhydrophobicity. Such nanostructured coatings may be useful for applications such as anti-fog coatings, self-cleaning surfaces, DNA manipulation, transparent electrodes for low-voltage electronics, and chemical and biological sensors.