Spin hydrodynamics -- recent developments

After briefly touching on relativistic hydrodynamics, we provide a detailed description of recent developments in spin hydrodynamics. We discuss the theory of perfect spin hydrodynamics within two different approaches, which lead to identical generalized thermodynamic relations. We also indicate the applicability range of the theory, finding it compatible with the conditions existing in the late stages of heavy-ion collisions. Finally, we discuss the near-equilibrium dynamics.