  We review the recent finding of the two-plateau momentum distribution of sea
quarks in deep inelastic scattering off nuclei in the saturation regime. The
diffractive plateau which dominates for small $\bp$ measures precisely the
momentum distribution of quarks in the beam photon, the r\^ole of the nucleus
is simply to provide an opacity. The plateau for truly inelastic DIS exhibits a
substantial nuclear broadening of the momentum distribution. Despite this
nuclear broadening, the observed final state and initial state sea quark
densities do coincide exactly. We emphasize how the saturated sea is generated
from the nuclear-diluted Weizs\"acker-Williams because of the anti-collinear
splitting of gluons into sea quarks.
