AGN accretion disk continua show temporal luminosity variations over the entire
wavelength range from X-rays to optical on time scales of days to years.  The continuum
variability induces the reverberation phenomena in the outer accretion disk, Broad Line
Region (BLR), and dust torus IR emission.  The reverberation mapping technique has been
used to put constraints on the radial extent and physical conditions of the otherwise
unresolved accretion disk, BLR, and dust torus around the central supermassive black
holes.  In this talk I will review the recent observational progress and emerging issues
in the AGN reverberation mapping.