SB 3.27.11

A pure devotee can see the presence of the Supreme Personality of Godhead in everything materially manifested. He is present there as reflection only, and a pure devotee can realize that in the darkness of material illusion the only light is the Supreme Lord, Personality of Godhead, and He is the support as it is confirmed in the Bhagavad-gita that the background of the material manifestation is Lord Krsna. And, as it is supported in the Brahma-samhita that Krsna is the cause of all causes and it is supported by the Brahma-samhita that the Supreme Lord by His partial or plenary expansion He is not only within the universe, each and every universe, but He is present in every atom although He is one without a second. The word used in this verse: advayam, "without a second," that means although the Supreme Personality of Godhead is represented in everything, including the atoms, He is advayam, it is not that He is divided. How He is present in everyting is explained in the next verse.