Pediatrics is a relatively new discipline; it came into existence at the end of the nineteenth century, when the number practitioners of medicine interested in the study and teaching of pediatrics grew in proportion to research in diseases of children. The study of two childhood diseases was instrumental in the very emergence of nephrology. The first disease was diarrheal dehydration of infants, the study of which in the first decades of the twentieth century provided much of the body of knowledge of water and electrolyte metabolism that formed the foundations of renal physiology. The second disease was the nephrotic syndrome of children, the successful treatment of which became possible after the Second World War with the use of adrenal cortical tropic hormone and steroids. The prohibitive cost of obtaining these new miracle drugs then led to the foundation in 1948 of the Nephrosis Foundation, which became the National Kidney Foundation (NKF) in 1950-the first organization in the United States dedicated to the support and dissemination of knowledge on diseases of the kidney. The Scientific Advisory Board of the NKF was the nidus around which the discipline of nephrology then evolved and, after the availability of maintenance hemodialysis, flourished. Pediatric nephrology, which emerged from these beginnings, closes the circle that began with the emergence of nephrology from its foundations in pediatric studies of childhood diarrhea and treatment of the nephrotic syndrome.