https://arstechnica.com/gadgets/2020/11/we-are-giddy-interviewing-apple-about-its-mac-silicon-revolution/

Some time ago, in an Apple campus building, a group of engineers got together. Isolated from others in the company, they took the guts of old MacBook Air laptops and connected them to their own prototype boards with the goal of building the very first machines that would run macOS on Apple's own, custom-designed, ARM-based silicon.