This turned up in my feed today, covering a book "Microcontroller Exploits".
While I am sure there are pointy heads on the forum to whom this is old hat, I found it fascinating.
I hasten to add I have zero connection with either the writer or the Youtube channel.
I once read (saw?) a story about one of the early microprocessors in the '70-ies or '80-ies. It buried a handful of transistors (or connections?) under other layers, and as a result their competitors were apparently delayed for half a year to reverse-engineer the silicon.