MicroRNA (miRNA) are small, non-coding RNA molecules that play a crucial role in regulating gene expression. Typically 20 to 24 nucleotides long, they bind to complementary sequences in messenger RNA (mRNA), leading to the degradation of the mRNA or inhibition of its translation into proteins. This process helps control various biological functions, including development, cell differentiation, and responses to stress. These tiny molecules are found in plants, animals, and some viruses, highlighting their importance across different life forms. Dysregulation of microRNA has been linked to various diseases, including cancer and cardiovascular disorders, making them a significant focus of research in molecular biology and medicine.