At the atomic level, where quantum physics takes over, electrons can indeed “tunnel” through from one side of a barrier to the other. In 1958 Leo Esaki, then at Tokyo Tsushin Kogyo (now Sony Corporation), demonstrated that tunneling through semiconductors (materials that have conductivity between a conductor and an insulator) was possible.

Subsequently Ivar Giaever from General Electrics proved that tunneling is also possible through superconductors (materials that have zero electrical resistance in extremely low temperatures). Giaever’s superconductor tunneling experiment inspired young theoretical physicist Brian Josephson to conduct in-depth analysis and predictions of what electrical currents do during tunneling. Josephson’s predictions eventually became known as Josephson’s effects. 

Esaki’s and Giaever’s experiments contributed greatly to the development of semiconductor research, scanning tunneling microscopy, quantum dots, and superconducting quantum interference devices. Josephson's theoretical discoveries led to the development of an entirely new method of studying quantum phenomena called quantum interferometry. Quantum interferometry has already been used in varied applications such as measuring temperatures near absolute zero, detecting gravitational waves, ore prospecting, communicating through water and through mountains, and studying the electromagnetic fields around the heart and the brain.

Esaki, Giaever, and Josephson received the Nobel Prize in Physics in 1973.