Very early in his career, while working in a remote marine biological laboratory in Italy, the young Otto Warburg observed that fertilization of sea urchin eggs resulted in a rapid and nearly sixfold increase in oxygen consumption (Warburg, 1908). The notion that oxygen consumption was dynamic and seemingly tied to cellular proliferation would have a profound effect on the young scientist. Later, these ideas would be refined and focused not on normal fertilization but rather on the metabolic abnormalities of cancer cells. Some 23 years after his observations in Italy, Warburg was awarded the Nobel Prize for his discovery of the “nature and mode of action of the respiratory enzyme.” Interestingly, although Warburg’s oocyte observations have been confirmed by many others, his hypothesis that this represented a burst of mitochondrial oxidative phosphorylation is undoubtedly incorrect. Indeed, nearly 100 years after his initial observation, it was established that the surge of oxygen consumption after fertilization is not, as originally envisioned, some primitive metabolic wakeup call by the young zygote. Rather, it would seem, oxygen is instead used by a specific NADPH oxidase on the egg’s surface for the purposeful production of nanomolar concentrations of hydrogen peroxide (Wong et al., 2004). Surprisingly, this burst of hydrogen peroxide production does not damage the nascent organism, but instead is used as part of an enzymatic reaction that ultimately results in the development of a protective shell around the young fertilized egg. These observations are in concert with a growing body of evidence that suggests that ROS can be purposefully made and harnessed to regulate a diverse array of physiological processes. In turn, accumulating evidence also suggests that dysregulation of oxidant signaling may cause or accelerate a host of pathological conditions, including the rate that we age (Balaban et al., 2005). Thus, seemingly from life’s inception to its end, redox signaling acts as an important regulator of physiological and pathophysiological outcomes. Herein, I will try to selectively review some of the highlights and emerging trends in oxidant signaling.