Reporter assays are experimental techniques used to measure the activity of specific genes or signaling pathways within cells. They typically involve the introduction of a reporter gene, such as luciferase or GFP, which produces a measurable signal when expressed. This allows researchers to assess how different conditions or treatments affect gene expression. These assays are widely used in molecular biology and drug discovery to study cellular responses to various stimuli. By analyzing the intensity of the signal generated by the reporter gene, scientists can gain insights into the regulatory mechanisms of transcription factors and other cellular processes.