The Gayatri mantra mentions: Bhur Bhuvaha Suvah - the Bhuloka, Bhuvarloka and Suvarloka (The human world, nether world and heaven). It is wrong to conceive of these three as existing one on top of the other. In fact the three lokas (worlds) are intertwined with each other and one exists within the other. The real meaning of this kind of geometrical configuration of the three lokas is that the pancha indriya, bhutas and koshas (five senses, elements and sheaths) that constitutes the body is Bhuloka; the aspect of prana shakti or manas thathvam (mind principle) is Bhuvarloka; and the microscopic state of Anandam (bliss) represents Suvarloka. So it can be said that the three worlds are nothing but thedeha thathwa, manas thathwa and Ananda thathwa (essential nature of body, mind and bliss) and the totality of these three represents the Trivikrama thathwa (nature of Vishnu expanding to the three worlds). (Divine Discourse, Sep 4, 1979.)