  Relaxed, massive galactic objects have been identified at redshifts z = 4;5;
and 6 in hydrodynamical simulations run in a large cosmological volume. This
allowed us to analyze the assembly patterns of the high mass end of the galaxy
distribution at these high zs, by focusing on their structural and dynamical
properties. Our simulations indicate that massive objects at high redshift
already follow certain scaling relations. These relations define virial planes
at the halo scale, whereas at the galactic scale they define intrinsic
dynamical planes that are, however, tilted relative to the virial plane.
Therefore, we predict that massive galaxies must lie on fundamental planes from
their formation.
  We briefly discuss the physical origin of the tilt in terms the physical
processes underlying massive galaxy formation at high z, in the context of a
two-phase galaxy formation scenario. Specifically, we have found that it lies
on the different behavior of the gravitationally heated gas as compared with
cold gas previously involved in caustic formation, and the mass dependence of
the energy available to heat the gas.
