 Oxygen can be transformed into reactive oxygen species, ROS, upon reaction with electrons, which have both harmful and beneficial effects on cells and health. While prolonged exposure to high ROS concentrations may lead to nonspecific damage, low-to-intermediate concentrations exert their effects through regulation of cell signaling cascades. ROS are involved in normal physiological processes such as redox regulation and biosynthetic processes, but can also cause disease due to a lack or surplus of ROS. Antioxidant supplementation has proven largely ineffective in clinical studies, while specific inhibition of ROS-producing enzymes is a more promising approach for clinical efficacy. This article was authored by Catherine Brieger, Stefania Shavoni, Francis J. Miller Jr., and others.