The discoverer of the causes of photochemical smog, Haagen-Smit was one of the founders of atmospheric chemistry, but first made significant contributions to the chemistry of essential oils. Haagen-Smit was born in Utrecht, Holland, in 1900, and graduated from the University of Utrecht. He became head assistant in organic chemistry there and later, served as a lecturer until 1936. He came to the United States as a lecturer in biological chemistry at Harvard, then became associate professor at the California Institute of Technology in Pasadena. He retired as Professor of Biochemistry in 1971, having served as executive officer of the department of biochemistry and director of the plant environment laboratory. Haagen-Smit also contributed to the development of techniques for decreasing nitrogen oxide formation during combustion in electric power plants and autos, and to studies of damage to plants by...