X-gal is widely used in molecular biology as a substrate for detecting β-galactosidase activity. It is particularly valuable in blue-white screening, a technique used to identify recombinant bacteria. When X-gal is cleaved by β-galactosidase, it produces an insoluble blue product, allowing researchers to visually distinguish between colonies with and without the enzyme. This makes it an essential tool in cloning experiments, where it helps identify successful insertion of DNA into vectors. Additionally, X-gal is used in histochemistry and cell biology to localize β-galactosidase activity in tissues or cells, aiding in the study of gene expression and cellular processes. Its specificity and ease of use have made it a staple in laboratories for decades.