RNA interference (RNAi) is a regulatory mechanism that makes use of small double-stranded RNA molecules for sequence-specific suppression of gene expression through translation or transcriptional repression. RNA interference is also known as post-transcriptional gene silencing. RNAi is an efficient, precise and stable method of gene suppression. Two types of RNA molecules are used for RNAi: microRNA and small interfering RNA (siRNA). RNAs are the direct products of genes and these small RNAs govern the enzyme complexes to degrade the mRNA. It prevents translation and decreases their activity via post-translational gene silencing. The various studies that are constantly contributing towards advancing techniques and evolution of this field are examined in detail in this book. Also included herein is a detailed explanation of the various concepts and applications of RNA interference. This book is a collective contribution of a renowned group of international experts.