RNA silencing is a pan-eukaryotic, sequence-specific gene regulation mechanism with recognized roles in development and maintenance of genome integrity. In plants, this mechanism also operates as a major antiviral defense system whereby 21-24 nt-long RNAs derived from the pathogen's genomes guide post-transcriptional silencing (PTGS) of viral transcripts. Recent evidence suggests that PTGS involving small RNAs of cellular, rather than pathogenous origin, might additionally have broad implications in potentiating basal defense and race-specific resistance to microbes in plants. These studies simultaneously unravel a staggering degree of complexity and flexibility in endogenous RNA silencing pathways, a likely reflection of the plants' faculty to adapt to their environment.