Ultrasmall chemical reactors can be created at the fused junctions of crossed polymer nanofibres, reports a study online in Nature Chemistry this week. This method enables reactions to be carried out on as few as 1,500 molecules, and could eventually be used to find potential leads for new drugs as part of the screening process involved in the initial stages of drug development. The ability to perform reactions on a very small scale is highly desirable because it reduces energy consumption, avoids potential problems associated with the toxicity of some starting materials, and minimizes the amount of waste material produced. Pavel Anzenbacher and Manuel Palacios made very small polymer fibres ― hundreds of times narrower than a human hair ― that contain different reactive molecules. The fibres are laid across one another and then either heated or exposed to solvent vapours, which fuses them together at the crossing points and allows a chemical reaction to occur between the reactive compounds they contain. This technique has the potential to be scaled down to the point where a reaction can be instigated between just two molecules ? one from each fibre. In an accompanying News & Views article, Andrew deMello and Rob Wootton say that "ultra-high-throughput reaction screening is unquestionably an achievable target" for the system described by Anzenbacher and Palacios.