Biological assays are laboratory tests used to measure the effects of substances on living organisms or biological systems. They help scientists evaluate the potency, efficacy, and safety of drugs, chemicals, or biological products. Common types of assays include enzyme assays, cell-based assays, and immunoassays, each designed to assess specific biological activities. These tests often involve comparing a sample against a standard to determine its biological activity. For example, a cell-based assay might measure how a new drug affects cell growth or survival. Biological assays are essential in fields like pharmacology, toxicology, and biotechnology for developing new therapies and ensuring safety.