RNA interference (RNAi) is a genetic regulatory mechanism that occurs in eukaryotic cells and regulates the activity of genes. Its main function is to suppress, silence or deactivate genes. RNAi can occur either naturally or artificially. It occurs naturally through the production of pre-miRNA. RNAi can also be induced experimentally by using double-stranded RNA (dsRNA). The synthetic dsRNA may be of two types: small hairpin RNA (shRNA) or short interfering RNA (siRNA). An enzyme known as DICER is necessary in both natural and artificial pathways for the formation of miRNA from pre-miRNA or for the formation of siRNA from shRNA. This book traces the progress of this field and highlights some of its key concepts and applications. It studies, analyses and upholds the pillars of RNA interference and its utmost significance in modern times. This book includes contributions of experts and scientists which will provide innovative insights into this field.