Here's how it happened:
* The Basilisk: The petrified students were victims of the Basilisk, a giant snake that could kill with a single glance, turning its victims to stone.
* The Fang: Harry Potter, with the help of Fawkes, Dumbledore's phoenix, obtained a Basilisk fang.
* The Tears: Fawkes, with its magical healing abilities, provided tears to counteract the Basilisk venom.
* The Cure: Harry applied the Basilisk fang to the petrified students while dripping Fawkes' tears onto the fang, reversing the petrification process.
This was a crucial moment in the story, demonstrating the power of love, sacrifice, and courage against darkness and fear.