MicroRNAs (miRNA) are small non-coding RNAs that regulate almost all biological processes, protein production, inflammatory responses, immune regulation, tumorigenesis and infection. In mammals, the classic formation of miRNA needs to transcribe a long primary miRNA in the nucleus and then process it into hairpin RNA with about 60–70 nucleotides. Eventually, this precursor miRNA will be transported to the cytoplasm for processing and shearing resulting in the generation of mature miRNA.