P-bodies, or processing bodies, are discrete cytoplasmic foci (chief centers of a morbid process) composed of messenger ribonucleic acid--protein complexes containing a subset of proteins involved in mRNA decay. Concentrated foci of mRNA decay enzymes were initially reported in mammalian cells and subsequently were further expanded in the yeast Saccharomyces cerevisiae. Recent studies indicate that P-bodies serve a dual functional role. In addition to mRNA decay, P-bodies are sites of mRNA storage for translationally silenced mRNAs, including noncoding microRNA-mediated translational silencing in mammals.