Each 'memory' is an ERC721 NFT that has been assigned to an ERC6551 token-bound account (TBA) address. Thanks to the TBA address, each memory can own 'items'

Each 'item' is an ERC721 NFT. An item represents the photos or videos that are part of the memory collection. To recap, an ERC721 memory can own multiple ERC721 items

This dapp demostrates the power and functionality of ERC6551 TBA addresses. You can create memories, add items to them, and donate ETH to the memory