He takes her to his Fortress of Solitude near the North Pole and shows her the traces of his past stored in the energy crystals of the Fortress, one of which is the green crystal that created the Fortress and opened Superman's contact with his parents.
He takes her to his Fortress of Solitude near the North Pole. He shows her the traces of his past, one of which is the green crystal. This past is stored in the energy crystals of the Fortress, one of which is the green crystal. This green crystal created the Fortress. This green crystal opened Superman's contact with his parents.