  Cold Fermionic atoms with three different hyperfine states confined in
optical lattices show pronounced Atomic Density Waves (ADWs). These ADWs are
pinned due to the confining potential that traps the atoms in the optical
lattice and can be considered a crystal of strongly bound trions. We show that
the crystalline phase is incompressible and robust against SU(3) symmetry
breaking interaction. We also show that it is generic in the presence of the
trap due to its incompressible characteristics. A simulation of the time
evolution of the fermionic gas after the trapping potential is switch off shows
that the formation of the trionic crystal is marked by a freezing of the
dynamics in the lattice.
