Quantum renormalization group scheme provides a microscopic understanding of
holography through a general mapping between the beta functions of underlying
quantum field theories and the holographic actions in the bulk. We show that
the Einstein gravity emerges as a long wavelength holographic description for a
matrix field theory which has no other operator with finite scaling dimension
except for the energy-momentum tensor. We also point out that holographic
actions for general large N matrix field theories respect the inversion
symmetry along the radial direction in the bulk if the beta functions of
single-trace operators are gradient flows with respect to the target space
metric set by the beta functions of double-trace operators.