ASML

ASML is a Dutch company that builds lithography machines: the equipment that prints circuit patterns onto silicon wafers. Making a chip involves many steps, but lithography decides how small the transistors can be. The machine shines light through a mask holding the circuit's pattern, shrinks it with optics and projects it onto the wafer, layer after layer.

Its most advanced machines use EUV (extreme ultraviolet) light, with a wavelength far shorter than visible light, which is what makes today's smallest transistors possible. ASML is the only company in the world that makes EUV machines. Each one is the size of a bus, costs roughly a couple of hundred million dollars, ships in many containers and takes months to install. TSMC, Samsung and Intel all depend on them for their leading-edge chips.

That monopoly turns ASML into a geopolitical piece. The machines rely on parts from a network of European, American and Japanese suppliers, and the Dutch government, coordinating with the United States, restricts which machines can be sold to China. Whoever cannot buy EUV machines cannot make the most advanced chips, whatever their designs.