RNA Interference (RNAi) technology has rapidly become one of the key methods used in functional genomics. RNAi is used to block the expression of genes and create phenotypes that can potentially yield clues about the function of these genes. In the postgenomic era, the elucidation of the physiological function of genes has become the rate-limiting step in the quest to develop 'gene-based drugs' and RNAi could potentially play a pivotal role in the validation of such novel drugs. In this overview, the basic concepts and applications of RNAi biology are discussed. Leading experts from both academia and industry have contributed to this invaluable reference. The volume is forwarded by Andrew Fire, one of the winners of the 2006 Nobel Prize for the discovery of RNA Interference.