Form factors and generalized hydrodynamics for integrable systems

Our review covers microscopic foundations of generalized hydrodynamics (GHD). As one generic approach we develop form factor expansions, for ground states and Gibbs ensembles (GGE). In the latter case so obtained results are compared with predictions from GHD. One cornerstone GHD GGE averaged currents, which can also be through employing factors. Discussed is a second, completely orthogonal based on availability self-conserved current.