The most celebrated and oft repeated story from Srimad Bhagavatam is the story of Prahlada.
The vile Hiranyakashipu, wanting to ask for death-less-ness, considering himself very smart, instead, asked for death, neither at day or at night, neither by man or beast, neither up nor down, so on and so forth. Hiranyakashipu was a great enemy of Vishnu and he had got this boon to avenge himself the death of his brother Hiranyaksha at the hands of Vishnu. It was indeed difficult to find a loophole in his boon and kill him by any creation of Lord Brahma. Having got his boon he went on to torture sages, people and divine and semi-divine beings for many yugas. Under his reign the world it seemed had forgotten Lord Vishnu. This however, as rightly pointed out by Prahlada himself (मन्ये धनाभिजनरूपतपःश्रुतौजस्तेजःप्रभावबलपौरुषबुद्धियोगाः । नाराधनाय हि भवन्ति परस्य पुंसो) did not seem to bother the Lord.
Ironically Prahlada, Hiranyakashipu’s own young son was a great devotee of Lord Vishnu and refused to acknowledge the greatness of his father as Supreme Being. This irritated Hiranyakashipu and he was even ready to kill his own son to prove his superiority. Such was his hatred which had won over his पुत्रवात्सल्य. Hence he threw Prahlada in fire, out of which he came without even a singed hair; he fed him poison which did not even make him drowsy; he pushed him from the mountain-top and Prahlada did not even have a scratch! Even after witnessing these miracles, Hiranyakashipu did not even have an inkling of the greatness of the Supreme being which was supporting his son. Then came the instance when he drew out his sword and asked Prahlada, “Show me that power which is supporting you!” Prahlada replied, “the very question you ask is by that Power.” “Alright then, where is it?” “Everywhere” “Everywhere! If it is everywhere, how come I don’t see it in this pillar? Let it come and save you” So saying he struck the pillar and out came Nrsimha in all his glory. Lord Vishnu incarnated as Nrsimha exclusively for Prahlada.
The little boy Prahlada was not afraid of the Lord, even though He looked gruesome and He had just killed his father. He went on to praise the Lord and thank him for his mercies.