One day Lord Kṛṣṇa as the naughty child disturbed His mother Yaśodā, and she began to tie up the child with ropes just to punish Him. But no matter how much rope she used, she found it always insufficient. Thus she became fatigued, but in the meantime the Lord opened His mouth, and the affectionate mother saw within the mouth of her son all the universes situated together.

[Srimad Bhagavatam -2.7.30-purport]