Historical Background - Modern (1900-present)
1900 AD Max Planck states his radiation law and Planck's constant.
1902 Rutherford and Frederick Soddy discover the law of radioactive decay.
1903 Rutherford and Soddy publish work on radioactivity as the transformation of atoms.
1905 Albert Einstein completes his theory of special relativity.
Einstein explains the photoelectric effect.
Einstein explains Brownian motion as due to molecular collisions.
1906 Hermann Walther Nernst presents a formulation of the third law of thermodynamics.
1908 Hans Geiger and Rutherford invent the Geiger counter.
1909 Rutherford and Royds demonstrate that alpha particles are doubly ionized helium atoms.
1911 (to 1913) Soddy, Russell, and Kazimir Fajans recognize the existence of isotopes among radioactive elements.
Rutherford proposes nuclear model of the atom.
1913 Henry Gwyn Moseley shows that nuclear charge is the real basis for numbering the elements.
Robert Millikan measures the fundamental unit of charge.
1915 Einstein completes his theory of general relativity.
1916 Lewis and Irving Langmuir formulate an electron shell model of chemical bonding.
Arnold Sommerfeld proposes elliptical orbits for electrons in atoms.
Niels Bohr proposes correspondence principle.
1919 Rutherford achieves the first artificial disintegration of a nucleus -- the transmutation of the nitrogen nucleus by alpha particle bombardment.
1924 Louis Victor De Broglie advances the wave theory of material particles.
Wolfgang Pauli proposes the exclusion principle.
1926 Erwin Schrödinger states his nonrelativistic quantum wave equation.
1927 Clinton Joseph Davission, Lester Germer, and George Thomson confirm the wavelike nature of electrons.
Werner Heisenberg states the quantum uncertainty principle.
Bohr formulates complementarity principle.
1932 Chadwick discovers the neutron.
John Douglas Cockcroft and Ernest Thomas Walton achieve the transmutation of elements by protons.
Anderson discovers the positron.
1934 Lawrence and Livingston construct the cyclotron.
Leo Szilard realizes that nuclear chain reactions may be possible.
1939 Otto Hahn and Fritz Strassman obtain the first atomic fission with uranium.
1942 Enrico Fermi makes the first controlled nuclear chain reaction.
The Manhattan Project is launched.
1945 First thermonuclear fission bomb exploded at Alamogordo in the New Mexico desert.
1946 The carbon-14 dating technique is developed by Willard Frank Libby. 
1952 The first hydrogen bomb, Mike, is detonated.
1953 Watson and Crick construct a three-dimensional model of the DNA molecule.
1972 Workers at Stanford University construct the first recombinant DNA molecules using restriction enzymes and DNA ligase.
1973 Public concern swell over the possibility of the production of potentially dangerous microorganisms by recombinant DNA technology.
1975 An international conference is held in Asilomar, California, urging strict guidelines regulating recombinant DNA research.
1977 Genentech, the first genetic engineering company, is founded to use recombinant DNA methods to produce medically important drugs.
1980 The Nobel Prize in Chemistry is awarded for the creation of the first recombinant DNA molecules and the development of powerful DNA sequencing methods.