  Radio emission in blazars -- the aligned subset of Active Galactic Nuclei
(AGN) -- is produced by synchrotron electrons moving relativistically in their
jet's magnetic field. Under the assumption of some degree of uniformity of the
field, the emission can be highly polarized -- linearly and circularly. In the
radio regime, the observed variability is in most of the cases attributed to
flaring events undergoing opacity evolution, i.e. transitions from optically
thick to thin emission (or vice versa). These transistions have a specific
signature in the polarization parameter space (angle and magnitude) which can
be traced with high cadence polarization monitoring and provide us with a
unique probe of the microphysics of the emitting region. Here we present the
full Stokes analysis of radio emission from blazars observed in the framework
of the F-GAMMA program and discuss the case study of PKS\,1510$-$089 which has
shown a prominent polarization event around MJD 55900.
