Genetic engineering, also known as recombinant DNA technology, is the deliberate manipulation of an organism's genome using biotechnological tools to alter its genetic material for specific purposes. It involves the introduction, deletion, or modification of genes within an organism to achieve desired traits that would not naturally occur through conventional breeding or natural evolution. In the context of drugs regulatory affairs, genetic engineering plays a pivotal role in the development, production, and regulation of pharmaceuticals, vaccines, and therapeutic proteins. The technique enables the production of biologics with enhanced efficacy, reduced side effects, and targeted therapeutic action, which requires meticulous regulatory oversight to ensure safety, efficacy, and ethical compliance. The fundamental process of genetic engineering typically involves several key steps. Initially, the gene of interest, which encodes a desired protein or function, is identified and isolated using molecular biology techniques such as restriction enzymes and polymerase chain reaction (PCR). This gene is then inserted into a vector, often a plasmid or viral genome, which can carry the gene into a host organism. Microorganisms, including bacteria, yeast, and filamentous fungi, are commonly used as host systems because of their rapid growth, well-characterized genetics, and ability to express foreign genes efficiently. Once the gene is introduced into the host, the microorganism expresses the protein or produces the compound encoded by the inserted gene. The final product is then extracted, purified, and subjected to rigorous quality control tests to ensure consistency, purity, and potency. Microorganisms are single-celled organisms, often microscopic, that include bacteria, archaea, yeasts, molds, and certain algae. These organisms exhibit remarkable genetic diversity, metabolic flexibility, and adaptability, making them indispensable tools in genetic engineering. In pharmaceuticals, microorganisms are harnessed for the production of antibiotics, vaccines, hormones, enzymes, and other biologically active compounds. For instance, recombinant bacteria like *Escherichia coli* are frequently engineered to produce insulin, growth hormones, and clotting factors. Yeasts such as *Saccharomyces cerevisiae* serve as hosts for producing vaccines, including subunit vaccines for viral infections. Filamentous fungi can be engineered to synthesize enzymes or secondary metabolites with medicinal properties. In all cases, the use of microorganisms requires stringent regulatory evaluation to ensure that genetically modified strains do not pose