The most basic gravitational stability analysis is the Jeans criteria, which addresses the balance between self-gravity and thermal pressure in a gas. In terms of the two above stability conditions, the system is stable if: i) thermal pressure balances the force of gravity, and ii) if the system is compressed slightly, the outward pressure force must become stronger than the inward gravitational force - to return the system to equilibrium. In the Jeans case, the stability criterion is size dependent, resulting in the concept of a Jeans length and Jeans mass.