  We investigate shadowing effects in deep-inelastic scattering from nuclei at
small values $x<0.1$ of the Bjorken variable. Unifying aspects of generalized
vector meson dominance and color transparency we first develop a model for
deep-inelastic scattering from free nucleons at small $x$. In application to
nuclear targets we find that the coherent interaction of quark-antiquark
fluctuations with nucleons in a nucleus leads to the observed shadowing at
$x<0.1$. We compare our results with most of the recent data for a large
variety of nuclei and examine in particular the $Q^2$ dependence of the
shadowing effect. While the coherent interaction of low mass vector mesons
causes a major part of the shadowing observed in the $Q^2$ range of current
experiments, the coherent scattering of continuum quark-antiquark pairs is also
important and guarantees a very weak overall $Q^2$ dependence of the effect. We
also discuss shadowing in deuterium and its implications for the quark flavor
structure of nucleons. Finally we comment on shadowing effects in high-energy
photon-nucleus reactions with real photons.
