A quintessential element in Hippocratic medicine is the theory of humors: The human body contains four basic substances, called humors. Their relative proportions in the human body regulate the human temperament and its behavioral manifestations, and their correct balance defines ‘health’. Hippocrates, a founding father of ancient-world medicine, systematically observed human temperaments and behaviors, and concluded that besides physiology, they are greatly influenced by environmental factors and geography, thus setting the stage for holistic approaches.