It has been known for 300 years that normal life is possible with a single kidney. Removal of both kidneys, however, leads to death within several days. Between these extremes is found the quantity of kidney sufficient for life. It was in 1888 that Theodore Tuffier was the first to address this question. A few years later, Carnot did his studies on growth factors that could influence kidney growth. This subject has not lost its interest. Today, the problem of progressive renal failure is studied by many investigators, from clinicians to basic scientists, specialists in cytokines and molecular biology. This article will define the origins of those efforts, an adventure which is ongoing today.