An RNA Microcosm

Abstract
A year ago came the suprising discovery that animals have perhaps hundreds of micro-RNAs (miRNAs). Now the importance of miRNA in plants and animals is being revealed. In his perspective, Baulcombe describes new work (Llave et al.; Hutvágner and Zamore) that gives insight into how miRNA and related small RNAs may control processes as diverse as translational arrest, RNA cleavage, and genome rearrangement.