The embed block the selection addresses: the node-selected block, the block at the caret, one of its ancestors, or, because inserting an embed leaves the caret just before it and atoms hold no caret of their own, the block right after the caret's.
The embed block the selection addresses: the node-selected block, the block at the caret, one of its ancestors, or, because inserting an embed leaves the caret just before it and atoms hold no caret of their own, the block right after the caret's.