  Selective amplification of the line and continuum source by microlensing in a
lensed quasar can lead to changes of continuum spectral slopes and line shapes
in the spectra of the quasar components. Comparing the spectra of different
components of the lensed quasar and the spectra of an image observed in
different epochs one can infer the presence of millilensing, microlensing and
intrinsic variability. Especially, microlensing can be used for investigation
of the unresolved broad line (BLR) and continuum emitting region structure in
active galactic nuclei (AGN). Therefore the spectroscopic monitoring of
selected lensed quasars with 3D spectroscopy open new possibility for
investigation of the BLR structure in AGN. Here we discuss observational
effects that may be present during the BLR microlensing in the spectra of
lensed QSOs.
