I love this from Chandogya Upanishad, 8.1: In the center of the castle of Brahman, our own body, there is a small shrine in the form of a lotus flower, and within can be found a small space. We should find who dwells there, and we should want to know him.
And if anyone asks, "Who is he who dwells in a small shrine in the form of a lotus flower in the center of the castle of Brahman? Whom should we want to find and to know," we can answer: The little space within the heart is as great as this vast universe. The heavens and the earth are there, and the sun, and the moon, and the stars; fire and lightening and winds are there; and all that now is and all that is not. For the whole universe is in Him and He dwells within our heart.