Micro-RNAs are small, non-coding RNA molecules that play a critical role in gene regulation. They're also known as miRNAs, a term coined by Victor Ambros and Gary Ruvkun, who discovered them in the nematode Caenorhabditis elegans in 1993. Other synonyms for micro-RNA include small RNA, non-coding RNA, small non-coding RNA, and regulatory RNA. They're different from messenger RNA (mRNA), which carries genetic information from the DNA to the ribosomes, where it's translated into protein. Instead, miRNA regulates gene expression by binding to mRNA molecules and inhibiting translation or promoting degradation. This process is crucial in many biological processes, including development, cell differentiation, and immune response.