P-bodies (processing bodies) are cytoplasmic foci visible by light microscopy in 
somatic cells of vertebrate and invertebrate origin as well as in yeast, plants 
and trypanosomes. At the molecular level, P-bodies are dynamic aggregates of 
specific mRNAs and proteins that serve a dual function: first, they harbour 
mRNAs that are translationally silenced, and such mRNA can exit again from 
P-bodies to re-engage in translation. Secondly, P-bodies recruit mRNAs that are 
targeted for deadenylation and degradation by the decapping/Xrn1 pathway. 
Whereas certain proteins are core constituents of P-bodies, others involved in 
recognizing short-lived mRNAs can only be trapped in P-bodies when mRNA decay is 
attenuated. This reflects the very transient interactions by which many proteins 
associate with P-bodies. In the present review, we summarize recent findings on 
the function, assembly and motility of P-bodies. An updated list of proteins and 
RNAs that localize to P-bodies will help in keeping track of this fast-growing 
field.