RNAi is a mainstay of contemporary biological research. But how exactly this crucial mechanism functions in humans remains a partial mystery that we are now one step closer to solving. Structural biologists have now published atomic-resolution pictures and a comprehensive analysis of the workings of a part of the RNAi machinery in Molecular Cell. They've discovered how several parts of the machinery work in concert to tamp down gene expression after the attachment of the machinery to an mRNA copied from a gene.