**Abstract**

MicroRNAs (miRNAs) are a class of short non-coding RNA molecules that are involved in development and diseases. Early studies are focusing on the miRNA profile as a biomarker in disease. As discovery of human miRNAs increased in the setting of disease, the research focus was gradually shifted towards miRNA therapeutic strategy for diagnostic and treatment of disease. Increasing evidences suggest that miRNAs are the next important class of antisense therapeutic molecules, which have significant advantage over antisense such as siRNAs because miRNAs are naturally occurring endogenous molecules. Aberrant alteration of the endogenous miRNAs has been linked to the development of certain diseases. Correcting these altered miRNAs by their mimics or inhibitors has been developed as potential therapeutic approaches. Some of the miRNA-based therapeutics are processed in preclinical and clinical trial for treatment hepatitis C, liver cancer, and other diseases. Currently, the major focus in the development of miRNA-based therapeutics is how to increase the miRNA stability and optimize delivery systems for specific disease with minimal off-target effect. This chapter will first overview the miRNA biogenesis, patho- and physiologic function, and regulation of miRNA molecules. Then, we discuss the miRNA-based potential therapeutic approaches and implication in disease.

**Keywords:** miRNA, function, disease biomarker, therapeutics
