The Board Summary for Trello extension retrieves and displays summary data for Trello boards. The board summary can include the number of active lists/cards in the board and a summary of due dates for cards in the board (past due/due now/due today/due soon). On board pages, the board summary data allows for creating nested boards, i.e. cards that reference other boards. Simply create a card whose description is the URL of another board, or use the add Nested Board button on the card edit page to pick an existing board or create a new board, and this card will be treated as an nested board. This method allows these cards to be usable in other browsers and mobile apps without this extension.