RNA Interference in Mammalian Cell Systems -- RNAi Pathway in C. elegans: The Argonautes and Collaborators -- Genetics and Biochemistry of RNAi in Drosophila -- Role of Dicer in Posttranscriptional RNA Silencing -- The Mechanism of RNase III Action: How Dicer Dices -- MicroRNA Metabolism in Plants -- Structure-Function Relationships Among RNA-Dependent RNA Polymerases -- RNAi-Mediated Chromatin Silencing in Fission Yeast -- A Role for RNAi in Heterochromatin Formation in Drosophila -- RNA-Mediated Transcriptional Gene Silencing in Human Cells -- RNA Silencing in Mammalian Oocytes and Early Embryos -- Identifying Human MicroRNAs. will follow