How computers work, from the atom up (2011)

The answer doesn’t actually lay out how electricity flowing through a bunch of NAND gates physically causes the computer/CPU to begin booting up.

There’s always a step missing in these types of answers,

step n: electricity begins to flow through gates

step n+1: ???

step n+2: Microcode execution begins

Presumably in step n+1 something happens to the chip, more than just heating it up, that causes a regular pattern which we would call the very first step of microcode booting up.