Those who realize the nature of emptiness also realize that their own nature is that of flux, change, and impermanence. They will directly experience that mind, body, and environment, are pervaded with a dynamic quality of emptiness. They will see buddha-nature. To deeply and fully realize buddha-nature is to become an arhat, a noble one who has attained cessation. It is to have the four characteristics of an arhat: (l) that all defilements have been purified, (2) that all that needs to be done has been done, (3) that all future rebirths have been exhausted, and (4) that liberation from karma and retribution has been achieved. This is realizing the true nature of emptiness.
Nirvana
Nirvana in Sanskrit means 'extinction-quiescence,' Extinction is the complete cessation of suffering and the termination of the samsaric cycle. Quiescence means that fundamental ignorance and its vexations have been stilled, extinguished, no longer arising. There are two levels of nirvana: nirvana with remainder and nirvana without remainder. An arhat who has realized nirvana with remainder has been liberated from all mental defilements but the body of retribution still remains. The body is still subject to the misfortunes that can befall a body, but this remainder does not have the ordinary person's vexation from having a body. The arhat still experiences painful events and difficult situations but being completely free from the klesas--desire, hatred, and delusion--the mind does not suffer. Such was the case With many of the Buddha's disciples who became enlightened.