  In this article, we review the recent discoveries of exotic phenomena in
graphene, especially superconductivity. It has been theoretically suggested for
more than one decade that superconductivity may emerge in doped graphene-based
materials. For single-layer graphene, there are theoretical predictions that
spin-singlet $d+id$ pairing superconductivity is present when the filling is
around the Dirac point. If the Fermi level is doped to the Van Hove singularity
where the density of states diverges, then unconventional superconductivity
with other pairing symmetry would appear. However, the experimental perspective
was a bit disappointing. Despite extensive experimental efforts,
superconductivity was not found in monolayer graphene. Recently, unconventional
superconductivity was found in "magic-angle" twisted bilayer graphene.
Superconductivity was also found in ABC stacked trilayer graphene and other
systems. In this article, we review the unique properties of superconducting
states in graphene, experimentally controlling the superconductivity in twisted
bilayer graphene, as well as a gate-tunable Mott insulator, and the
superconductivity in trilayer graphene. These discoveries have attracted the
attention of a large number of physicists. The study of the electronic
correlated states in twisted multilayer graphene serves as a smoking gun in
recent condensed matter physics.
