Reines, Frederick (1918-1998), an American physicist, discovered a fundamental particle called the neutrino. The most notable qualites of the neutrino are that it is extremely resistant to interaction with other particles and has virtually no mass. The existence of neutrinos had been suggested many years before by the Austrian physicist Wolfgang Pauli, but it took 25 years to prove their existence experimentally. For his work on the neutrino, Reines was awarded half of the 1995 Nobel Prize for physics.