MicroRNAs are single-stranded RNAs of 19–25 nucleotides in length. MicroRNAs have emerged as central post- transcriptional repressors of gene expression. MicroRNAs have been implicated in regulation of cellular processes such as differentiation, proliferation, apoptosis, metabolism, haematopoiesis, cardiogenesis. MicroRNAs represent a class of genes with a great potential for use in diagnosis, prognosis, therapy and are a new frontier for molecular medicine.