  Remarkably rich physics is involved in the behavior of hybrid Josephson
junctions, connecting high-Tc and low-Tc superconductors. This relates in
particular to the different order parameter symmetries underlying the formation
of the superconducting states in these materials. Experiments on high-Tc/low-Tc
contacts have also played a crucial role in settling the decade-long d-wave
versus s-wave debate in cuprate superconductors. Recently, such hybrid
junctions have enabled more detailed pairing symmetry tests. Furthermore, with
these junctions, complex arrays of pi-rings have been realized, enabling
studies on spontaneously generated fractional flux quanta and their mutual
interactions. Steps toward novel superconducting electronic devices are taken,
utilizing the phase-shifts inherent to the d-wave superconducting order
parameter. This paper is intended to reflect the current status of experiments
using high-Tc and low-Tc Josephson contacts.
