Modern life would be very, very different if it weren't for photolithography, a very simple step in the processes for making an integrated circuit. Essentially, you use a slide projector to project an image of the circuit pattern on a wafer. Exposing the wafer to a light pattern modifies a chemical layer on top of the wafer, creating a mask. The mask allows selected parts of the wafer to be processed to create the circuit.
Despite its relative simplicity, photolithography is the limiting step that governs the rate at which power consumption drops, speed goes up, and the number of transistors increases. As you might imagine, a lot of people have spent a lot of time trying to improve or replace photolithography with a history of success.