MicroRNA or miRNA is a type of small, regulatory RNA that does not code for protein. Instead, it regulates gene expression by inhibiting the translation of mRNA into protein. MicroRNAs are produced by the cleavage of a double-stranded RNA precursor molecule with a hairpin turn. The two strands separate, and one becomes the mature miRNA, which is around 22 nucleotides long. The mature miRNA forms a complex with a group of proteins called the RNA-induced silencing complex or RISC. RISC binds to mRNA through complementary base pairing between the miRNA and specific sequences in the mRNA, typically in the 3-prime untranslated region. This pairing is usually not perfect, but it is enough to inhibit translation through cleavage and destruction of the mRNA or interfere directly with the translation process. Silencing of gene expression in either pathway is an important type of post-transcriptional regulation. Dysregulation of miRNA is correlated with potentially deadly diseases, such as cancer and heart disease