  The Cosmic Microwave Background (CMB) provides a precious window on
fundamental physics at very high energy scales, possibly including quantum
gravity, GUTs and supersymmetry. The CMB has already enabled defect-based
rivals to inflation to be discarded, and will be able to falsify many
inflationary models. In combination with other cosmological observations,
including those of high-redshift supernovae and large-scale structure, the CMB
is on the way to providing a detailed budget for the density of the Universe,
to be compared with particle-physics calculations for neutrinos and cold dark
matter. Thus CMB measurements complement experiments with the LHC and
long-baseline neutrino beams.
