microRNA Biogenesis and Function -- Regulation of pri-miRNA Processing Through Smads -- Stimulation of pri-miR-18a Processing by hnRNP A1 -- KSRP Promotes the Maturation of a Group of miRNA Precuresors -- Hormonal Repression of miRNA Biosynthesis Through a Nuclear Steroid Hormone Receptor -- Autoregulatory Mechanisms Controlling the Microprocessor -- Regulation of pre-miRNA Processing -- The Effect of RNA Editing and ADARs on miRNA Biogenesis and Function -- miRNAs Need a Trim -- Properties of the Regulatory RNA-Binding Protein HuR and its Role in Controlling miRNA Repression -- Turnover of Mature miRNAs and siRNAs in Plants and Algae -- MicroRNases and the Regulated Degradation of Mature Animal miRNAs. Given this pervasiveness and importance of miRNA-mediated gene regulation, it should come as little surprise that miRNAs themselves are also highly regulated. However, the recent explosion of knowledge on this topic has been remarkable, providing a primary motivation for publication of this book. As miRNAs are transcribed by RNA polymerase II, the enzyme that also generates mRNAs, it was perhaps not unexpected that miRNA transcription would be subject to regulation, and we have willfully mitted this aspect from this monograph. However, what has been unexpected is the extent of post-transcriptional regulation of miRNAs that is illustrated in this book.