The Hanle effect has been extensively used for the determination of th
e magnetic field strength and direction in solar prominences. Here we
address the problem of the diagnostics of weak magnetic fields in the
solar photosphere and chromosphere by means of their Hanle effect in s
ome selected absorption lines. As this is a relatively new area we wil
l focus on the diagnostic methods and summarize some results that rela
te to the presence of a weak, turbulent magnetic field in the photosph
ere and to the chromospheric magnetic canopy. Finally we will outline
some directions for future work.