Yukawa Institute for Theoretical Physics
Atomic nuclei consist of protons and neutrons held together by a strong force. Hideki Yukawa assumed that this force is borne by particles and that there is a relationship between the range of the force and the mass of the force-bearing particle. In 1934, Hideki Yukawa predicted that this particle should have a mass about 200 times that of an electron. He called this particle a "meson". Mesons' existence was verified in later experiments.