microRNAs are small, non-coding RNA molecules that play a crucial role in regulating gene expression. They are typically about 20-25 nucleotides long and function by binding to messenger RNA (mRNA) molecules, which can prevent the production of proteins or lead to their degradation. This process helps control various biological functions, including development, cell differentiation, and responses to stress. These tiny molecules are found in many organisms, including plants and animals, and are involved in numerous cellular processes. Dysregulation of microRNAs has been linked to various diseases, including cancer and cardiovascular disorders, making them important targets for research and potential therapeutic interventions.