Abstract
Small RNA guides--microRNAs, small interfering RNAs, and repeat-associated small interfering RNAs, 21 to 30 nucleotides in length--shape diverse cellular pathways, from chromosome architecture to stem cell maintenance. Fifteen years after the discovery of RNA silencing, we are only just beginning to understand the depth and complexity of how these RNAs regulate gene expression and to consider their role in shaping the evolutionary history of higher eukaryotes.
