  We review experiments on small-capacitance Josephson junctions. When the
Josephson junction is fabricated in the configuration of dc superconducting
quantum interference device (SQUID), the Josephson coupling can be tuned IN
SITU with an external magnetic field. The electrical transport properties of
one-dimensional arrays of small-capacitance dc SQUIDs have been investigated in
order to study the superconductor-insulator transition. The arrays have also
been used to bias a single Josephson junction, and a clear Coulomb blockade of
Cooper-pair tunneling has been observed in the single junction.
