In 1920s, Otto Warburg described the phenomenon of aerobic glycolysis, the ability of tumour cells to convert glucose to lactate in the presence of normal oxygen conditions. Warburg 's hypothesis of an altered metabolism in cancer cells found no immediate acceptance, though it was latter confirmed for most human tumours. With the advent of molecular biology the focus in tumour research has shifted towards the search for oncogenes. However, the interest in cancer molecular profiling eventually led to a renaissance of the Warburg effect trying to combine genetic alterations with effects on metabolism with the help of modern analytic technologies to rapidly analyze broad varieties of metabolites in various tissues and bodyfluids (metabonomics).