In this issue of Epigenetics

There has never been, in my opinion, a more expansive time in the history of biological studies. The sequencing of hundreds of organismal genomes coupled with the latest " omics " approaches have opened up new vistas that have revolutionized our view of biology. Nowhere is this more apparent than in the field of gene regulation, where a host of newly discovered mechanisms are now known to control where and when genes are turned on and off, and how these regulatory states are passed from one generation to the next. In many cases, the information potential of DNA is controlled by protein molecules that set up and lock in repressive or active regions of the genome. Increasingly, these regulatory mechanisms and complexes are being found to involve RNAs, including long non-coding RNAs (lncRNAs) and short non-coding RNAs (e.g., microRNAs and piRNAs). Knowledge of their involvement increases our view of the complexity of gene regulation but also opens some new opportunities for harnessing this newly discovered mechanism for useful purposes, for example, in medicine. Not only have microRNAs and other non-coding RNAs recently emerged as key regulators of gene expression during development, but they are also frequently mis-expressed in human disease states. Non-coding RNAs are increasingly being found to have causal roles in disease (e.g., in cancer, they have the ability to behave like oncogenes or tumor suppressors). These RNAs act to promote or repress cell proliferation, differentiation and death, homeostasis, and migration during development, all processes that go wrong in disease. Their molecular properties (and in some cases small size) make non-coding RNAs amenable as targets and therapeutics in disease treatment using standard antisense technologies. Non-coding RNAs thus provide the physician with a potentially powerful new battery of agents to diagnose and treat disease. However, while hundreds of human microRNAs and non-coding RNAs are known, relatively little is known about their roles, mechanisms and targets. We consider it extremely timely to dedicate an entire issue of Epigenetics to the topic of non-coding RNAs in epigenetics, with 12 reviews and 7 original research papers from prominent experts in the field to enjoy. Here is a preview of what you will find in this issue. A series of 6 reviews nicely outlines the links between non-coding RNAs and epigenetic changes to chromatin. Peschansky and Wahlestedt (p. 3) describe the classification of long and short non-coding RNAs and their interactions with proteins in …