Researchers keep discovering new functions of small RNAs. For instance, they can be used as a defense mechanism against viruses or self-replicating genome invaders. These tiny pieces of RNA are often produced by a cleavage of long precursors by so called Dicer proteins. To their surprise, researchers from the University of Bern have found that some Dicers acquired a unique and as yet unknown feature that allow them to cleave the RNA precursors in a very specific way, resulting in small RNAs that work much more efficiently.