Viral vectors are tools commonly used in molecular biology and genetic engineering to deliver genetic material into cells. They are engineered viruses that have been modified to remove their ability to cause disease, but retain the ability to infect cells and introduce specific genes or DNA sequences into the host cell's genome. Viral vectors are used in research to study gene function, develop gene therapies, and create genetically modified organisms. They are widely used in gene therapy to treat genetic disorders, cancer, and other diseases by delivering therapeutic genes into the patient’s cells. Viral vectors can be derived from a variety of viruses, including adenoviruses, lentiviruses, retroviruses, and adeno-associated viruses. Each type of virus has its own advantages and limitations in terms of capacity for gene delivery, ability to infect different cell types, and immune response elicited by the host organism. Overall, viral vectors are powerful tools in molecular biology research and hold great potential for medical applications in gene therapy and personalized medicine.