Small interfering RNA, or siRNA, is a type of RNA molecule that plays a crucial role in the regulation of gene expression. It is typically about 20-25 nucleotides long and works by binding to specific messenger RNA (mRNA) molecules, leading to their degradation. This process effectively silences the expression of certain genes, making siRNA a powerful tool in research and potential therapies. In the laboratory, scientists can design siRNA to target specific genes associated with diseases, allowing for precise manipulation of gene activity. This technology has applications in various fields, including genetics, molecular biology, and medicine, particularly in developing treatments for conditions like cancer and viral infections.