RNA performs a remarkable range of functions in all cells. In addition to i
ts central role in information transfer from DNA to protein, it is essentia
l for functions as diverse as RNA processing, chromosome end-maintenance an
d dosage compensation. The versatility of RNA derives from its unique abili
ty to use direct readout via base-pairing for sequence specific targeting (
or templating) in combination with its capacity to form elaborate three dim
ensional structures. Such structures can perform catalysis or serve as prot
ein recognition surfaces. In this short review, we attempt to give a flavor
for the diversity of functional RNAs in the cell and highlight, using sele
cted examples, two quite distinct activities, catalysis and sequence specif
ic targeting. Within each section. we discuss how the lessons we have learn
ed from these systems may apply to other, less well understood, RNAs.