Florian Hollfelder's group, together with colleagues in the Department of Chemistry, have published a paper in Nature Chemistry entitled "Evolution of enzyme catalysts caged in biomimetic gel-shell beads". Natural evolution relies on improvement of molecules by successive rounds of diversification and selection. In the laboratory, directed evolution has emerged as a powerful tool for the development of new and improved molecules, but it is limited by the enormous work and cost of screening. In this paper the groups produced gel-shell beads (GSBs) with the help of a microfluidic device. These hydrogel beads are surrounded with a polyelectrolyte shell that encloses an enzyme, its encoding DNA and the fluorescent reaction product. Active clones in these man-made compartments can be identified readily by high-speed fluorescence-activated sorting. This system was used to perform the directed evolution of a phosphotriesterase (a bioremediation catalyst) caged in GSBs. A 20-fold faster mutant could be isolated in less than one hour.