[3]Morphologists are biologists specializing in the structure of organisms or in the study of whole organisms. Biochemists, by contrast, study chemical reactions of biological materials. [4]This is not to be confused with a cell nucleus. This word was borrowed from biology for atomic theory, however. [5]An exception is the hydrogen atom, which has no neutron in its nucleus. [6]Mev is the abbreviation for million electron volts. [7]A concept for which James D. Watson of the United States and Francis H. C. Crick of England shared a Nobel Prize in 1962. [8]The study of tissues. [9]There are additional, more subtle metabolic events that lead to the synthesis of DNA, but they are not important in this discussion. PHOTO CREDITS Figure 1 Armed Forces Institute of Pathology Negative No. 4156 Figure 3 Dr. T. Tahmisian, Argonne National Laboratory Figure 4 Oak Ridge National Laboratory (photo on right) Figure 5 Oscar W. Richards, American Optical Company Figure 7 Brookhaven National Laboratory Figure 9 Battelle-Northwest Laboratory Figure 10 Oak Ridge National Laboratory Figure 19 Argonne National Laboratory Figure 23 Argonne National Laboratory Figure 24 Argonne National Laboratory Figure 28 Argonne National Laboratory Figure 29 Brookhaven National Laboratory This booklet is one of the “Understanding the Atom” Series. Comments are invited on this booklet and others in the series; please send them to the Division of Technical Information, U. S. Atomic Energy Commission, Washington, D. C. 20545. Published as part of the AEC’s educational assistance program, the series includes these titles: