A cell-based assay is a laboratory technique used to study the effects of substances on living cells. This method allows researchers to observe how cells respond to drugs, toxins, or other compounds, providing valuable information about their biological activity. By measuring changes in cell behavior, such as growth, death, or signaling pathways, scientists can assess the potential therapeutic effects of new treatments. These assays are essential in drug discovery and development, as they help identify promising candidates for further testing. They can also be used to evaluate the safety and efficacy of pharmaceuticals and biologics, making them a crucial tool in the field of biomedical research.