https://www.cnet.com/news/iphone-xs-industry-first-a12-chip-gives-apple-big-advantage-over-rivals/

It's thin, obviously. But it's still thick enough that you could fit about 10,000 of an A12's electronic components across its width. That miniaturization is a "huge breakthrough," Apple marketing chief Phil Schiller boasted on Wednesday, saying the A12 is the industry's first chip to be built using a 7-nanometer manufacturing process.

A nanometer is a billionth of a meter, so when Apple moved from the A11 chip's 10nm process to the A12's 7nm, it meant the company could stuff twice the number of circuit elements called transistors into the same surface area. In the case of the A12, that's 6.9 billion transistors.