  Large thickness of heavy nuclei brings in a new scale into the pQCD
description of hard processes in nuclear environment. The familiar linear
$k_{\perp}$-factorization breaks down and must be replaced by a new concept of
the nonlinear $k_{\perp}$-factorization introduced in \cite{Nonlinear}. I
demonstrate the salient features of nonlinear $k_{\perp}$-factorization on an
example of hard dijet production in DIS off heavy nuclei. I also discuss
briefly the non-linear BFKL evolution for gluon density of nuclei.
