  We review the present status of the experimental and theoretical research on
the proximity effect in heterostructures composed of superconducting (S) and
ferromagnetic (F) thin films. First, we discuss traditional effects originating
from the oscillatory behavior of the superconducting pair wave function in the
F-layer. Then, we concentrate on recent theoretical predictions for S/F layer
systems. These are a) generation of odd triplet superconductivity in the
F-layer and b) ferromagnetism induced in the S-layer below the superconducting
transition temperature $T_{c}$ (inverse proximity effect). The second part of
the review is devoted to discussion of experiments relevant to the theoretical
predictions of the first part. In particular, we present results of
measurements of the critical temperature $T_{c}$ as a function of the thickness
of F-layers and we review experiments indicating existence of odd triplet
superconductivity, cryptoferromagnetism and inverse proximity effect.
