An apoptosis assay is a laboratory test used to measure the process of programmed cell death, known as apoptosis. This process is crucial for maintaining healthy tissue by eliminating damaged or unnecessary cells. The assay helps researchers understand how cells respond to various treatments, such as drugs or environmental stressors, and can indicate whether a substance promotes or inhibits apoptosis. There are several methods for conducting an apoptosis assay, including flow cytometry, TUNEL staining, and caspase activity assays. Each method provides different insights into the stages and mechanisms of apoptosis, allowing scientists to study its role in diseases like cancer and to develop targeted therapies.