The breakthrough science of RNA-based functional modulation — RNA interference (RNAi) — was recognized by the award of the 2006 Nobel Prize in Medicine to Drs. Andrew Fire and Craig Mello. They demonstrated that the genetic information encoded in DNA within a cell could be blocked, in its translation to protein, through the action of RNA which can be either synthetic or naturally occurring small molecules such as microRNAs.

miRNAs are critical components in all biological systems, being highly conserved both across species and through evolutionary history. Through the mechanism of regulating gene expression, the regulatory RNAs, including miRNAs, play critical roles in modulating cellular activities, influencing phenotypes and susceptibility to disease (pathogenesis).

See this recent Nature documentary on RNA interference.