Abstract The year 2016 marks the centenary of the death of Elie Metchnikoff, the father of innate immunity and discoverer of the significance of phagocytosis in development, homeostasis and disease. Through a series of intravital experiments on invertebrates and vertebrates, he described the role of specialised phagocytic cells, macrophages and microphages, subsequently renamed neutrophils and polymorphonuclear leucocytes, in the host response to injury, inflammation, infection and tissue repair. As a vigorous proponent of cellular immunity, he championed its importance versus humoral immunity in the so-called antibody wars. By 1908, when the Nobel Prize was awarded to Elie Metchnikoff and Paul Ehrlich, this debate was not yet resolved. Even earlier, Metchnikoff had turned his research interests to the process of ageing and the possible link to intestinal auto-intoxication, giving rise to the current interest in the microbiome of the gut and the use of probiotics to promote health and longevity. During the past century, Metchnikoff's reputation has waxed and waned, as lymphocyte heterogeneity, specificity and memory began to dominate the field of adaptive immunity, yet his benign visage continues to provide an iconic presence for specialists in innate immunology, whose studies have made a striking comeback in the past decade. In this review, I shall consider the nature of his studies and the person as well as the legendary description of his Eureka experience in Messina in 1882, a story loved by students and investigators alike, that marked, in his own words, his transformation from zoologist to pathologist.