You are most likely doing thermodynamics. The simplest example would be the Kinetic Gas Theory also known as the Ideal Gas Equation.
In a fixed volume like a metal container, gases can exert pressure at different temperatures (Gay-Lussac's Law).
In a changing volume, you will have a balloon or a piston where the volume changes via gaseous expansion.
Solids do have a smallest volume. Try cooling the object to absolute zero . In theory, particles would have zero kinetictic energy and would not vibrate or move at all. Scientists are not exactly sure it this is the only thing that would happen.
I have heard that the International Space Station will be adding a machine that would cool things to record low temperatures (very close to