Introduction
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Apart from glucose, creatinine is the most common analyte in clinical chemistry. Even in the beginning of the 21st century, the majority of clinical laboratories refer to the 'Jaffe method' when assaying creatinine. The method is still in use 125 years following the discovery of the principle, which is a fact unparalleled in clinical chemistry. Despite the advent of the enzymatic creatinine analysis, the Jaffe method is still popular due to its simplicity and low cost. However, few people are aware that, in fact, Max Jaffe never published an analytical method, but rather he discovered the nature of urinary compounds, reactive with picric acid in an alkaline environment. The following paper highlights the discovery of Jaffe and its consequences.

Max Jaffe\'s life
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Max Jaffe (often misspelled as Jaffé) was bornin Grünberg in Silesia (nowadays Zielona Gora in Poland) on 25 July 1841. He was a German pharmacologist, biochemist and pathologist of Jewish descent. He received his medical education in Berlin, where he qualified in 1862. Ludwig Traube and Wilhelm Kühne were among his academic teachers. While still a student, he took a keen interest in chemical investigations and worked in the pathological laboratory under the direction of W. Kühne. Travel during his studies took him to Prague, Vienna and Paris. Thereafter, he became an assistant in the medical clinic at Königsberg in East Prussia from 1865 to 1872 under Ernst von Leyden, with whom he published a work on putrid sputum. This led to the discovery of the spirilla and leptothrix characteristic of putrid processes in the