The number of accessible microstates for degrees of freedom maximizes when larger particles lay adjacent to the wall and smaller particles distribute in the remaining phase space. The system seeks a configuration in which some particles with degrees of freedom sacrifice their microstates for the collective increase in microscopic degrees of freedom of the whole system. Essentially, it is the accessible states for each degree of freedom that causes randomness in the motions of particles, and consequently, the mysterious concept of entropy. It is known that a time-evolving system favors a configuration that maximizes accessible states, and therefore, maximum entropy -until it reaches the equilibrium state from an initial given nonequilibrium configuration.