MicroRNAs (miRNAs) are a large and important class of regulatory RNAs that silence target mRNAs through an antisense mechanism. They function in diverse developmental processes such as apoptosis and cell differentiation, and their dysregulation has been implicated in various diseases, especially cancers. We are particularly interested in addressing three key questions in the field: i) how do miRNAs function mechanistically; ii) how are the miRNAs themselves regulated; and iii) what are the developmental functions of specific miRNAs? We also pursue questions of general interest in RNA metabolism. Our long-term goal is to understand these processes quantitatively.