Justus von Liebig (1803-1873), German chemist. Liebig was born into a middle-class family and showed an early interest in chemistry. He was apprenticed to an apothecary before studying at the University of Bonn. He went on to Pris where he met Gay-Lussac and Cuvier, before himself becoming Professor of Chemistry at Giessen at the age of 21. He established laboratory-based teaching and was a gifted if harsh lecturer. His research demonstrated that organic chemistry could be replicated and analysed in the laboratory. He showed that nitrogen based compounds were essential to plant growth, and he invented the first nitrogen fertilisers. His Law of the Minimum stated that plants each have a mineral that regulates their development. With Giebert he devised a method of creating a beef extract from carcasses as a dietary supplement, the bouillon cubes of which were later trademarked as 'Oxo'.