  Fluctuations exist in any material object $A$. If $A$ has non-zero
temperature $T$, one speaks about thermal fluctuations. If $A$ is at very low
$T$, the fluctuations are of quantum origin. Interesting effects appear if two
bodies $A$ and $B$ are separated by a fluctuating medium $C$ (say a vacuum, or
a fluid close to its {\it critical point}) when the fluctuations are
long-ranged, i.e., they decay according to a power-law with the distance. Then
the changes of fluctuations in $C$ due to the surfaces and constituents of $A$
are also felt by $B$, and \textit{vice versa}, which leads to a fluctuation
induced force (FIF) between them. This force persists in addition to the direct
influence of $A$ on $B$ (say, via gravity or Coulomb's force). These FIF's can
be of attractive or repulsive character. They may play crucially important role
on phenomena involving objects with length scale comparative with the Universe,
as well as to the tiny objects relevant for MEMS and NEMS. In the current
article we present some basic facts for the FIF and their diversity. Then on
the example of one dimensional Ising model with a defect bond we present some
new analytical results for such forces.
