  In this talk, I discuss how we may approach physics at the seesaw- and
GUT-scales using data from the TeV scale. Even though we cannot hope to
directly reach these energy scales using particle accelerators, we may get
convinced of grand unification and seesaw mechanism based on experimental data
if Nature is kind to us. In addition, we may find compelling reason to believe
in leptogenesis based on experimental data. This cannot be achieved by a single
experiment, but rather a collection of them, based on LHC, ILC, neutrino
oscillation, neutrinoless double beta decay, direct dark matter detection, CMB
power spectrum and its tensor mode.
