Wendell Meredith Stanley (1904-1971) was awarded one quarter of the 1946 Nobel Prize in Chemistry for his crystallization and purification of enzymes and viral proteins. Through his research on the virus that causes mosaic disease in tobacco plants, Stanley isolated a nucleoprotein – protein associated with either DNA or RNA – that provided insight into how the virus causes the disease. The virus, which acted like an inanimate chemical, proved to be a living and growing organism instead. Later, Stanley studied influenza viruses and developed the centrifuge-type influenza vaccine. Stanley also led important work on diphenyl stereochemistry and the chemistry of the sterols.