  We discuss magnetism in spinor quantum gases theoretically and experimentally
with emphasis on temporal dynamics of the spinor order parameter in the
presence of an external magnetic field. In a simple coupled Gross-Pitaevskii
picture we observe a dramatic suppression of spin dynamics due to quadratic
Zeeman ''dephasing''. In view of an inhomogeneous density profile of the
trapped condensate we present evidence of spatial variations of spin dynamics.
In addition we study spinor quantum gases as a model system for thermodynamics
of Bose-Einstein condensation. As a particular example we present measurements
on condensate magnetisation due to the interaction with a thermal bath.
