Analogy for the World of Material Existence
 

Krishna speaking to Arjuna :

'It is said that there is an imperishable banyan tree that has its roots upward and its branches down and whose leaves are the Vedic hymns. One who knows this tree is the knower of the Vedas.'

'The branches of this tree extend downward and upward, nourished by the three modes of material nature. The twigs are the objects of the senses. This tree also has roots going down, and these are bound to the fruitive actions of human society.'

'The real form of this tree cannot be perceived in this world. No one can understand where it ends, where it begins, or where its foundation is. But with determination one must cut down this strongly rooted tree with the weapon of detachment. Thereafter, one must seek that place from which, having gone, one never returns, and there surrender to that Supreme Personality of Godhead from whom everything began and from whom everything has extended since time immemorial.'

from Bhagavad-Gita Chapter 15