The Front Panel is assembled from the outside inward:
The PANEL is the top-level container, or parent, for the entire Front Panel.
The PANEL is a container for one or more BOXes.
A BOX is a container for one or more CONTROLs.
There are two special types of containers:
A SUBPANEL is associated with a particular control (the control is the container for the subpanel). Subpanels "slide up" from the control with which they are associated.