The Dalai Lama's Little Book of Wisdom: The Essential Teachings

begin quote from page 52:

"In Tantric practice we find a lot of the emphasis placed upon the process of death, so that the individual at the time of death not only retains his or her presence of mind, but also is in a position to utilize the subtle state of consciousness effectively towards the realization of the path."

Continuing:

"From the Tantric perspective, the entire process of existence is explained in the three stages known as "Death", the "intermediate state" and "rebirth". All of these three stages of existence are seen as states or manifestations of the consciousness and the energies that propel the consciousness, so that the intermediate state and rebirth are nothing other than various levels of the subtle consciousness and energy.

An Example of such fluctuating states can be found in our daily existence, when during the 24 hour day we go through a cycle of deep sleep, the waking period and the dream state. Our daily existence is in fact characterized by these three stages."


end quote ending page 53.