Those who study the history of science and technology understand the important symbiotic relationships that exist between the various disciplines, and how a breakthrough in one area can trigger a chain reaction that leads to even more important progress in another area of science. This has certainly occurred in the discovery of triazine-resistant weeds in the late 1960's, followed in 1973 when Stanley Cohen of Stanford University and Herbert Boyer of the University of California at San Francisco found a simple way to combine DNA from two different organisms and then to clone identical copies of these recombined DNA molecules in bacteria. In 1975, Steven Radosevich made the important observation that isolated chloroplasts from triazine-resistant weeds were not inhibited in their rate of photosynthesis when treated with atrazine. With the use of triazine-resistant weeds and their chloroplasts, our knowledge of the structure of chloroplasts (herbicide binding genes that control the various peptides and amino acid sequences) and many other aspects of photosynthesis has expanded greatly during the past 10 years, with major contributions by Charles Arntzen and many other scientists.