Marceli Nencki was a great Polish scientist of the XIX century. He began his research at the University of Berne, Switzerland, in 1872. In 1876 he was appointed Associate Professor there, and one year later he became a full Professor and Director of the Institute of Medical Chemistry. In 1891 Marceli Nencki accepted an invitation to organize, together with Ivan P. Pavlov, the Institute of Experimental Medicine in St. Petersburg, where he spent the last decade of his life. In research he concentrated on topics related to urea synthesis, the chemistry of purines, and biological oxidation of aromatic compounds. He also examined the structure of proteins, enzymatic processes in the intestine, and bacterial biochemistry. Among Nencki’s greatest successes was showing, together with Leon Marchlewski, a close chemical relationship between hemoglobin and chlorophyll. The idea to establish the research institute named after Marceli Nencki was born shortly after his death in 1901. Among his friends who pushed forward this idea, the most effective was Nadine Sieber-Shumova, his close co-worker from Berne and St. Petersburg. However, many years were to pass until fi nally in 1918/19 the Nencki Institute was founded. Today, the Nencki Institute, where the neurobiology, neurophysiology, biochemistry and cell biology are widely represented, is the only research centre in Poland where the investigations are performed from the molecular to the whole animal and human subject level.