  Invariant manifolds provide the geometric structures for describing and
understanding dynamics of nonlinear systems. The theory of invariant manifolds
for both finite and infinite dimensional autonomous deterministic systems, and
for stochastic ordinary differential equations is relatively mature. In this
paper, we present a unified theory of invariant manifolds for infinite
dimensional {\em random} dynamical systems generated by
  {\em stochastic} partial differential equations. We first introduce a random
graph transform and a fixed point theorem for non-autonomous systems. Then we
show the existence of generalized fixed points which give the desired invariant
manifolds.
