You probably heard about free radicals, and why you should eat anti-oxidants to stay healthy. But have you heard of Reactive Oxygen Species? Chances are that you haven’t. But to cite a well-known on-line dictionary: Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. They are generally very small molecules and are highly reactive due to the presence of unpaired valence shell electrons. ROSs form as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling.