On the Cover: The cover of this Special Issue devoted to reactive oxygen species illustrates the transformation of oxygen to water, through reactive oxygen intermediates. This process begins with the monovalent reduction of oxygen to superoxide, followed by the dismutation of superoxide to form hydrogen peroxide, and the subsequent breakdown of hydrogen peroxide to form a hydroxyl radical and hydroxyl ion (not shown). The center image is a luminescent Arabidopsis plant expressing the oxidative stress-reporting construct ZAT12:LUC. This plant was treated with the herbicide methyl viologen prior to imaging. The plants surrounding the highenergy focal point symbolize the growing knowledge that reactive oxygen species play an important role in diverse processes in plants, ranging from response to biotic and abiotic stress to control of development. The cover was rendered by Ms. Jocelyn Brimo of the Center for Plant Cell Biology at the University of California, Riverside.