A Pensieve is a magical object found in the Harry Potter universe. It's a shallow stone or metal basin engraved with runes and symbols, used to view memories. When in use, it emits a silvery light and contains a substance that appears to be a cloudy liquid or gas, which are the stored memories. One can siphon their excess thoughts or memories into the Pensieve and then examine them at leisure, providing a way to spot patterns and links within the memories. It's particularly associated with the character Albus Dumbledore, who used it to review memories and teach Harry Potter about them..