You may already be aware that computer chips less than the size of your fingernail can contain over 50 billion devices with 7nm technology. Manufactures will start producing chips with devices the size of 3nm and they have 1nm devices on the drawing board.
A “device” in this case is a logic device (AND, NOT, OR, etc) which is made up of transistors, which are two or three part silicon components with traces of other elements.
This article talks about stacking them. Instead of a two dimensional layout, they could cluster certain combinations of devices in a three dimensional pattern.
If you take this to its logical development, you might think that rather than a paper thin cpu, you might have one the thickness of a penny with a million times more processing power.
But that is kind of where we are now, and average cell phone has more than a million times the processing power of the computer used in the Apollo craft that landed on the moon.
BTW, Moore’s law predicts that computer processing power will double every two years. That builds up really fast.