Matthew Meselson organized the Herbicide Assessment Commission in 1970, which investigated the use of Agent Orange and other defoliants in Vietnam. The work of the commission helped to end Operation Ranch Hand, in which the United States sprayed nearly 20 million gallons – about 73 million liters - of herbicides and defoliants over the rainforest and mangrove forest canopies of Vietnam, Laos and Cambodia. I called Meselson to ask about his role in the Herbicide Assessment Commission, along with a host of other fascinating investigations to do with chemical and biological weapons, such as the anthrax accident in the Soviet Union and the yellow rain incident in Laos. I also asked him about the U.S. Army's insane plan in 1969 to ship 800 railroad cars filled with 27,000 tons of poison-gas weapons from the Rocky Mountain Arsenal to New Jersey for disposal at sea. Meselson completed his Ph.D. in 1957 under Linus Pauling at CalTech. In 1958, in a classic experiment, he and Frank Stahl showed that DNA is replicated semi-conservatively, and in 1961 he along with Francois Jacob and Sydney Brenner discovered messenger RNA. Meselson also made fundamental discoveries in DNA repair, the recognition and destruction of foreign DNA in cells, and, along with Werner Arber, he discovered restriction enzymes. Meselson received his appointment as an Associate Professor of biology at Harvard in 1960 and his full professorship in 1964. He has been at Harvard ever since. Meselson has received many prominent awards throughout his career, including from the National Academy of Sciences, the Federation of American Scientists, the New York Academy of Sciences, and the Genetics Society of America, as well as the Guggenheim Fellowship and MacArthur Fellows Program Genius Award.