A comprehensive collection of cutting-edge methods for elucidating the function of new genes and altering gene expression. These readily reproducible techniques can be used either in transient and stable gene splicing applied to worms, flies, trypanosomes, mammals, and plants, or in studying RNA editing mechanisms in a wide range of organisms, including systems that involve the conversion of one base to another and insertion/deletion editing. Topics of interest include stable and transient RNA interference, gene silencing, RNA editing, bioinformatics, small noncoding RNAs, and RNomics. Special attention is given to methods for the identification and characterization of small RNAs involved in RNA interference or modification.