We present here the work done by us in last one year and also our future plans. We are
working on two projects : radio to optical cross-correlation study of the blazar PKS 2155-304
and the x-ray intra-day variability of blazars with Nuclear Spectroscopic Telescope Array
(NuSTAR). In the optical part of our first project we generated ~ 12 years optical R-band
light curve of the blazar PKS 2155-304. By using the structure function (SF) and the auto-
correlation function (ACF), we found eight possible periods which indicate two possibilities:
an optical periodicity of ~ 311 days and multiple periods with their harmonics. We also
generated more than three dozen light curves of blazars using NuSTAR data. We performed
SF analysis and also estimated excess variance for these light curves.