Droplet microfluidic systems provide a controlled environment in which to perform rapid mixing, isolation of picoliter size fluid volumes and rapid variation of reaction conditions. Indeed, the ability to controllably form droplets with variable reagent composition at high speed lies at the heart of performance improvements when compared to conventional microfluidic devices operating under laminar flow conditions. Furthermore, it is important to realize that segmented-flow systems can generate droplets at rates in excess of 1 kHz. In theory, this means that millions of individual reactions or assays can be processed in very short times. In addition, since mixing is rapid and reagent transport occurs with no dispersion, microdroplet reactors are superior environments in which to study biological reactions, especially rapid kinetic reactions, when compared to diffusion-limited continuous-flow formats. Accordingly, droplet microfluidics is a promising technology to perform reactions and assays in a high-throughput manner, in which a hugely productive and efficient system for screening a desired component from thousands of samples is necessary.