Yes, of course, but only if the controls in questions are true windows, in the sense of Windows API.
Not all controls are like that. Some controls in some libraries are not implemented as window objects. They are implemented in pure graphics, using, say, GDI+, DirectX, or some other access to graphics. In such approach, some host control (panel, window) is really a window object, but inner controls are based on accessing graphics and events of this host control. Sometimes, such approach to UI is called "lightweight". In a way, such "lightweight" control simply don't exist from the standpoint of Windows API; instead they are all represented by a single host control, all at once.
If you want to drill down to the control which are real Windows API window object, you need to use… Windows API. This single method would do the most of the job:
As you can see, if you only have the HWND of some top-level window, you can dig out all child windows hierarchically placed in this main window.