  Ultrafast pump-probe spectroscopy is a powerful tool to study the
nonequilibrium dynamics in high-Tc cuprate superconductors. The photo-induced
quasiparticle (QP) dynamics revealed by pump-probe spectroscopy are sensitive
to the near-Fermi level electronic structures. Here we review several selected
examples to illustrate the enduring challenges including pairing glue, phase
separation, and phase transitions in cuprate superconductors. We also present
the data obtained on thin films of YBa2Cu3O7-{\delta} in connection to these
issues.
