Curiosity to see the illusory energy of the lord sometimes develops into sinful material desire.
“Satisfied by the prayers Śrī Mārkaṇḍeya had offered, the Supreme Lord told him to ask for a benediction, and the sage said he wanted to see the Lord’s illusory energy. The Supreme Lord Śrī Hari, present before Mārkaṇḍeya in the form of Nara-Nārāyaṇa, smiled ruefully, because He prefers that His pure devotees stay away from His illusory energy. Curiosity to see the illusory energy of the Lord sometimes develops into sinful material desire. Nonetheless, to please His devotee Mārkaṇḍeya, the Lord granted his request, just as a father who cannot convince his son to give up pursuing a harmful desire may let him experience some painful reaction so that he will then voluntarily desist. Thus, understanding what would soon happen to Mārkaṇḍeya, the Lord smiled as He prepared to display the illusory potency to him and then left for Badarikāśrama. One day, as Śrī Mārkaṇḍeya was offering his evening prayers, the water of devastation suddenly flooded the three worlds. With great difficulty Mārkaṇḍeya moved about all alone in this water for a long time, until he came upon a banyan tree. Lying upon a leaf of that tree was an infant boy glowing with a charming effulgence. As Mārkaṇḍeya moved toward the leaf, he was pulled by the boy’s inhalation and, just like a mosquito, drawn within His body.
Inside the boy’s body, Mārkaṇḍeya was amazed to see the entire universe just as it had been before the annihilation. After a moment the sage was carried out by the force of the child’s exhalation and hurled back into the ocean of annihilation. Then, seeing that the child on the leaf was actually Śrī Hari, the transcendental Lord situated within his own heart, Śrī Mārkaṇḍeya tried to embrace Him. But at that moment Lord Hari, the master of all mystic power, disappeared. Then the waters of annihilation disappeared as well, and Śrī Mārkaṇḍeya found himself in his own āśrama, just as before.”
Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Twelth Canto, Chapter 09 – Intro & Text 07.