The production of a biologic drug substance material initially yields a solution that contains both the desired therapeutic protein and a variety of impurities, which range from viruses to misfolded proteins. Because impurities reduce the drug’s safety and efficacy, the final drug solution to be used by patients must contain only the desired therapeutic protein. Therefore, purification operations are performed to remove impurities during the manufacture of a biologic drug substance. This scrollable interactive explains the general role of purification operations in the production of a biologic. It explores 3 purification operations that are used to inactivate and remove viral impurities—viral inactivation, viral filtration, and ultrafiltration and diafiltration. It also examines the metrics that are used to determine if each purification operation has been completed successfully.