  Magnetic fields on the surface of the Sun and stars in general imprint or
modify the polarization state of the electromagnetic radiation that is leaving
from the star. The inference of solar/stellar magnetic fields is performed by
detecting, studying and modeling polarized light from the target star. In this
review we present an overview of techniques that are used to study the
atmosphere of the Sun, and particularly those that allow to infer magnetic
fields. We have combined a small selection of theory on polarized radiative
transfer, inversion techniques and we discuss a number of results from
chromospheric inversions.

Solar and Stellar Astrophysics