Twenty-five years ago it was possible to predict that many more RNAs that were known at that time would be found: Some of them would be catalytic and some of them would not be but would serve other functions. The prediction turned out to be spectacularly true and this book deals with one class of novel RNAs, the microRNAs (miRNAs). The task now is to elucidate the nature and function of all these new RNAs.

This book is a compendium of experimental methods, in silico and the traditional kind, of analyzing the miRNAs. There are many chapters on miRNAs on intra-cellular functions, in developmental events and in disease. A newcomer would do well to have this volume handy for purposes of reference and for its educational value per se. There are not many books on miRNAs that have such an extensive and complete view of the field as it now exists. My hope is that the problems presented here will be worked on assiduously to pave the way for a new synthesis of various RNAs as important regulatory genes in eukaryotes.