Thomas Graham (1805-1869), who is credited with seminal work on the nature of the diffusion of gases and of osmotic forces in fluids, can properly be called the father of modern dialysis. His apparatus to study the behavior of biological fluids through a semipermeable membrane clearly presaged the artificial kidney in clinical use today. In 1913, John Abel and coworkers reported the first application of the principles of diffusion to remove substances from the blood of living animals. Unaware of Abel's work, Georg Haas (1886-1971) performed the first human dialysis in the German town of Giessen in 1924. But it was not until 1945 that Willem Johan Kolff, working under extremely difficult wartime conditions in The Netherlands, achieved the first clinically successful hemodialysis in a human patient.