In Node Viewers
Node Viewers of Components can be set to be Geometry Viewers. A Component must have its Node View parameter set to Geometry Viewer (found on the Misc page of the Component's parameters). These geometry viewers do not include all the toolbars of a Geometry Viewer in a pane, however you can access many options by pressing 'p' over the viewer while in Viewer Active mode.
Any Pane can be set to Geometry Viewer using the pane type menu or by using the shortcut alt+3.