American biochemists Martin Kamen and Sam Ruben discovered carbon-14, a radioactive isotope of carbon, which is now used extensively as the basis of the radiocarbon dating method to date archaeological and geological samples.

Martin David Kamen was an American chemist who, together with Sam Ruben, co-discovered the synthesis of the isotope carbon-14 on February 27, 1940, at the University of California Radiation Laboratory, Berkeley. He also confirmed that all of the oxygen released in photosynthesis comes from water, not carbon dioxide, in 1941.

Samuel Ruben was an American chemist who with Martin Kamen co-discovered the synthesis of the isotope carbon-14 in 1940.

Carbon-14, C-14, ¹⁴C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples. Carbon-14 was discovered on February 27, 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California. Its existence had been suggested by Franz Kurie in 1934.

A radionuclide is a nuclide that is unstable and known to undergo radioactive decay into a different nuclide, which may be another radionuclide or be stable. Radiation emitted by radionuclides is almost always ionizing radiation because it is energetic enough to liberate an electron from another atom.

Radiocarbon dating is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.