RRC ‐ reporter ready cells are transfected with a luciferase reporter gene which is expressed upon activation of stress pathways e.g. NFκB inflammation response or Nrf‐2 antioxidant response. The cells have been frozen right after transfection in a way that they are ready‐to-use for the reporter gene assay instantly after thawing. The cells are immediately responsive to the respective stress inductors. There is no need to cultivate or passage the cells before use.