The shadow root is attached to another node tree through a specific DOM node referred to as its host . This host may be part of another shadow tree or part of the regular DOM tree. The node tree of a shadow root's host is sometimes referred to as the light tree .

The hidden DOM nodes of a shadow tree are generally not affected by anything applied outside the shadow tree, and vice versa. The shadow boundary , where the shadow DOM ends and the regular DOM begins, can be traversed, but only very intentionally:

• Scripting shadow tree nodes from outside requires the use of a special Shadow DOM API to be accessed.
• Styling a shadow tree from outside can be achieved via CSS scoping and CSS shadow parts .