Fibre-top cantilevers are a new generation of miniaturized devices obtained by carving tiny mechanical beams directly on the cleaved edge of an optical fibre. The light coupled from the other side of the fibre allows measurements of the position of the cantilever with sub-nanometre accuracy. The monolithic structure of the device, the absence of electronic contacts on the sensing head, and the simplicity of the working principle offer unprecedented opportunities for the development of scientific instruments for both standard applications and utilization beyond research laboratories. In this paper we review the results that our group has obtained over the last year in the development of this technology. We describe the working principle and the fabrication procedure, and we present a series of proof-of-concept experiments that demonstrate that fibre-top cantilevers can be used both for atomic force microscopy and for the detection of chemical species. © 2007 IOP Publishing Ltd.