Justus von Liebig (1803-1873) was a German chemist who made major contributions to agricultural and biological chemistry, and worked on the organization of organic chemistry. He devised the modern laboratory-oriented teaching method and is regarded as one of the greatest chemistry teachers of all time. He is known as the "father of the fertilizer industry" for his discovery of nitrogen as an essential plant nutrient, and his formulation of the Law of the Minimum which described the effect of individual nutrients on crops. He died in 1873 at the age of 69.