  Gamma-ray Bursts can be used as distance indicators using the Combo relation.
We show how the proposed THESEUS mission will allow us to investigate the
evolution history of the Universe at high redshift with GRBs. Assuming that
THESEUS will measure the redshift for 800 GRBs, we show that the accuracy on
the cosmological parameters of the main cosmological models will greatly
improve, so that we can use GRBs as additional and independent cosmological
probes and also put strong constraints on the evolution of the dark energy
equation of state parameter $w(z)$.
