  The Transient High Energy Sky and Early Universe Surveyor (THESEUS) is a
space mission concept aimed at exploiting Gamma-Ray Bursts for investigating
the early Universe and at providing a substantial advancement of
multi-messenger and time-domain astrophysics. A fundamental contribution to
achieve this goal will be provided by the powerful synergy between THESEUS and
the extremely large ground-based telescopes which will operate in the next
decade, like E-ELT. We discuss great improvements coming from this joint effort
and describe some possible observing scenarios.
