Computers have become much more compact and increasingly powerful largely because of lithography, a basically photographic process that allows more and more features to be crammed onto a computer chip.

Lithography is akin to photography in that it uses light to transfer images onto a substrate. Light is directed onto a mask-a sort of stencil of an integrated circuit pattern-and the image of that pattern is then projected onto a semiconductor wafer covered with light-sensitive photoresist. Creating circuits with smaller and smaller features has required using shorter and shorter wavelengths of light.