  The features of electron assisted neutron exchange processes in crystalline
solids are survayed. It is stated that, contrary to expectations, the cross
section of these processes may reach an observable magnitude even in the very
low energy case because of the extremely huge increment caused by the Coulomb
factor of the electron assisted processes and by the effect of the
crystal-lattice. The features of electron assisted heavy charged particle
exchange processes, electron assisted nuclear capure processes and heavy
charged particle assisted nuclear processes are also overviewed. Experimental
observations, which may be related to our theoretical findings, are dealt with.
The anomalous screening phenomenon is related to electron assisted neutron and
proton exchange processes in crystalline solids. A possible explanation of
observations by Fleischmann and Pons is presented. The possibility of the
phenomenon of nuclear transmutation is qualitatively explained with the aid of
usual and charged particle assisted reactions. The electron assisted neutron
exchange processes in pure $Ni$ and $Li-Ni$ composite systems (in the
Rossi-type E-Cat) are analyzed and it is concluded that these reactions may be
responsible for recent experimental observations.
