Edward Calabrese, Professor of Toxicology at the University of Massachusetts, Amherst: The story of the dose response in biology and medicine seems like it should be simple and straight-forward. Yet,it is far from either, displaying a series of remarkably unique historical stages with each being controversial and highly contentious, in a struggle that has always been about what is the nature of the dose response in the low dose zone. This paper is about the history of the dose response and how its diverse scientiﬁc roads lead to hormesis. However, there have been major episodes, or stages in the history of the dose response and multiple battles fought over the nature of the dose response in the low dose zone, affecting careers, national economies, health and safety regulations, the testing of chemicals and drugs and whether, if and when neuron saving drugs will transform human health. NOTE: USE YOUR BROWSER TEXT SIZE OPTION TO INCREASE ARTICLE TEXT SIZE FOR EASIER READING.