Investigation of active galactic nuclei in time domain era
  The perfect case for time-domain investigations are active galactic nuclei
(AGNs) since they are luminous objects that show strong variability. Key result
from the studies of AGNs variability is the estimated mass of a supermassive
black hole (SMBH), which resides in the center of an AGN. Moreover, the
spectral variability of AGN can be used to study the structure and physics of
the broad line region, which in general can be hardly directly observed. Here
we review the current status of AGNs variability investigations in Serbia, in
the perspectives of the present and future monitoring campaigns.
