宇
=
于
+
宀
:
Yu the Great (yu) just earned her PhD in the space station (Ø3) and is proudly putting on her graduation cap (宀). She was measuring cosmic (宇) rays by investigating the traces they left in a honey jar (于) and is demonstrating her experiment for the camera.
宙
=
宀
+
由
:
James II of England (zh) finds that he forgot his cuba libre (由) in the outhouse's bathroom (ou4) during the last party. A lot later he finds that in the glass a whole new universe (宙) has developed. He writes a thesis about it and earns a PhD, proudly wearing a graduation cap (宀).