But it’s now so difficult that the number of companies with the knowledge and cash to do it is about to shrink to precisely four.

The factories in which microchips are made, called fabs, can cost billions of dollars. They’re like rocket launch sites or nuclear power plants: Everyone knows where they are and how many are in the works. And they make the microchips on which all nearly all advanced smartphones, PCs, servers, and other critical pieces of IT infrastructure depend.

The smallest elements on the most advanced microchips, currently in testing, are down to 14 nanometers, on the scale of atoms and molecules.