A Josephson Junction is a quantum device made of two superconductors separated by a thin insulating barrier. It allows for the flow of supercurrent, which is a current that flows without any voltage applied. This phenomenon occurs due to the quantum tunneling of Cooper pairs, which are pairs of electrons that move together through the superconductor. These junctions are crucial in various applications, including quantum computing and superconducting qubits. They enable the development of highly sensitive magnetometers and are essential components in Josephson voltage standards, which provide accurate voltage references in metrology.