This issue of Nature Reviews Genetics sees the launch of a new Article Series on Non-coding RNA (ncRNA).

We start the Series with two new Reviews that look at two very different aspects of ncRNA biology. On p846, Eugene Berezikov explores the evolution of animal microRNAs and what this particularly celebrated class of ncRNAs has contributed to the evolution of increasingly more complex organisms. A diverse range of approaches — from phylogenomics to biochemistry — have contributed to our understanding in these areas.

In a second Review on p861, Manel Esteller looks at the roles of ncRNAs in human disease. Initially, this field of research focused on miRNA dysregulation in cancer. But it is becoming increasingly apparent that a diverse range of ncRNAs — from small nucleolar RNAs (snoRNAs) to long non-coding RNAs (lncRNAs) — have crucial functions in disease. The disorders in which ncRNAs and their machineries have been implicated span from neurological disorders with Mendelian patterns of inheritance to complex conditions, such as cardiovascular disease.

Despite the relatively long history of research on the roles of miRNAs in cancer, we clearly still have much to learn, even in this regard — as underlined by the Research Highlight on p804. This article discusses three new studies that reveal extra layers of complexity to microRNA regulation, in which the interactions of miRNAs with their targets — including an important tumour suppressor gene — are modulated by other mRNAs and ncRNAs.

More articles on the diverse roles of ncRNAs can be found online at the Series homepage (http://www.nature.com/nrg/series/noncoding), including Reviews on the functions of ncRNAs in embryogenesis and the use of RNAi for therapy.