Californium is a synthetic element with the atomic number 98 and the symbol Cf. It was first synthesized in a laboratory in the USA in 1950 by a team of scientists led by Glenn T. Seaborg. Californium is highly radioactive and is one of the most expensive elements to synthesize. Its isotopes have a variety of applications, including as a neutron source for research purposes and as a radiation source in nuclear measurements. Californium-252 is used in nuclear reactors to start fission reactions and to produce electricity. Additionally, it has potential uses in cancer therapy. Though it is not widely available due to its rarity and high cost, Californium has a number of applications in research and nuclear energy.