MicroRNAs (miRNAs), endogenous noncoding regulatory mRNAs of - nucleotides, have rapidly emerged as the central players in gene expression regulation. Owing to their ever-increasing implications in the control of various biological and pathological processes, miRNAs have now been considered novel biomarkers of various human diseases including, cancer, viral disease, cardiov- cular disorders, metabolic disturbances, etc. Particular expression pro?les have been associated with particular pathological states. Expression pro?ling of miR- NAs have therefore become extremely important not only for fundamentalists but also for clinicians. However, the methodologies used for detecting protein-coding mRNAs cannot be directly applied to miRNAs because of their small size. Over the past years, researchers have made great efforts to developing techniques suitable for miRNA detection and quanti?cation; a wide spectrum of creative and inno- tive techniques (more than 30 different methods) have been invented and validated. It has come to the time now to summarize these methods and present them in an orderly manner for better understanding and utilization of these methods to miRNA research and applications. In particular, the development of methods for quantifying circulating miRNAs opens up a fascinating opportunity for realizing miRNA as diagnostic and prognostic biomarkers of human disease. A book on this subject may help boosting up the passion of researchers to further improve the existing techniques and develop more new methods to ?t to new application needs. These considerations prompted us and urged us to undertake the work: writing a book focusing on miRNA expression detection methods.