"The answer was right here." Dumbledore stood up, went around the desk, passed Harry, and came to a freestanding, three-tiered metal storage cabinet in the room, gleaming gold and shaped like a magnificent castle. It was crammed with transparent, candle-like crystal bottles, and inside the clear crystal bottles floated a swirling, silvery-white substance.
"What you see here are all memories," Dumbledore said, pointing to one crystal bottle in the cabinet. "This little bottle contains a memory concerning Tom Riddle."
Hearing this, Harry stepped forward and saw that the label on the bottle Dumbledore was pointing at read "Tom Riddle."
The gray stone Pensieve flew out of the storage cabinet and landed on the headmaster's desk. Dumbledore shared with Harry this memory about Tom Riddle's family.
After coming out of the Pensieve, Harry stood by the desk, digesting everything he had just seen and heard.
What disgusted Harry even more was that Dumbledore also told him the Gaunt family was an extremely ancient wizarding family, notorious for restlessness and violence. Because they had made a habit of marrying within the family, that behavior had caused the family's traits to grow more pronounced with each generation. They lacked reason, and coupled with a particular fondness for lavish show, the family fortune had been squandered long before Marvolo's time, generations earlier. Harry was shocked to discover that Voldemort's maternal grandfather, Marvolo Gaunt, had a terrifyingly foul temper, yet was also arrogant and conceited beyond reason. He valued his ancestral relics far more than his son Morfin or his daughter Merope.
Thinking of Voldemort's background, Harry felt that, compared with him, he seemed far luckier. Though he too was an orphan, he certainly did not have a grandfather and uncle who had attacked Muggles and even Ministry of Magic officials, and had finally been