One of the first studies on the energy metabolism of a tumour was carried out, in 1922, in the
laboratory of Otto Warburg. He established that cancer cells exhibited a specific metabolic
pattern, characterized by a shift from respiration to fermentation, which has been later
named the Warburg effect. Considerable work has been done since then, deepening our
understanding of the process, with consequences for diagnosis and therapy. This review
presents facts and perspectives on the Warburg effect for the 21st century.