  Formation of eta-mesic nucleus, a bound state of an eta meson in a nucleus,
is reviewed in this paper. Three different theoretical approaches are used to
calculate the binding energies and widths of such nuclei. The effect of
eta-mesic nucleus in pion double-charge-exchange reaction is discussed.
Experimental efforts by different groups to detect the nucleus are also
discussed. The ramifications of the theoretical and experimental studies of the
bound state of eta in a nucleus are pointed out.
