The Stone of Memories is an item which allows its user to travel back into the past.
It is a stone via fragments of the Stone of Memories. The stones are in the respective color shades of the users.
In "Young Fairies Grow Up," in order to learn more about the Digmole's secret, Faragonda brings the Winx and Roxy to the Hall of Memories and reveals to them the Stone of Memories, an item which allows its user to travel back into the past. Faragonda splits the stone into seven individual stones and entrusts them to the Winx and Roxy. Using the Stones of Memories, the Winx and Roxy travel to Alfea of the past to learn more about the secret of the Digmoles.
In "Butterflix," the Winx and Roxy use their stones to back to the present.