~Tulku Urgyen Rinpoche
We also need to clearly understand what is meant by the tenns 'samsara' and 'nirvana.' Nirvana means the fully realized buddha nature that consists of Body, Speech and Mind aspects. The Body is the essence that simply is. Speech is its nature, the cognizant quality that is vividly present. And Mind is the capacity, which is radiant.
These three aspects comprise the basic presence of all buddhas. They are none other than their essence, nature and capacity. All sugatas are of this same identity. In the same way, samsara is the body, speech and mind of all sentient beings, which are the deluded expressions of their essence, nature and capacity. In this way, dharmadhatu encompasses all of samsara and nirvana.
Dharmadhatu is adorned with dharmakaya, which is endowed with dharmadhatu wisdom. This is a brief but very profound statement, because 'dharmadhatu' also refers to sugata-garbha or buddha nature. Buddha nature is all-encompassing: this means it is present or basic to all states, regardless of whether they belong to samsara or nirvana.