  Real physical systems are often maintained off equilibrium by energy or
matter flows. If these systems are far from equilibrium then the
thermodynamical branch become unstable and fluctuations can lead them to other
more stable states. These new states are often endowed with higher degrees of
organization. In order to explore whether an energy-flow in combination with
self-gravity can lead to complex, inhomogeneous structures, like observed in
the interstellar medium (ISM), we perform N-body simulations of
self-gravitating systems subjected to an energy-flow. Moreover we perform some
simple gravo-thermal N-body experiments and compare them with theoretical
results. We find negative specific heat in an energy range as predicted by
Follana & Laliena (1999).
