Is it possible to make screenshot of a panel window For example I want to make a screenshot of a panel window "Fonts" in Mail. But I can't do it, because panel window is hidden when its parent app is not in foreground and to make screenshot of it, I need to open "Preview" first.

So, is it possible?
Use shortcut cmd+T to show the Font window

To take a screenshot using a manual rectangular selection, use cmd+Shift+4.

To take a screenshot using an automatic selection, press space as well.