In May 2013, Cymer was acquired by ASML Holdings of The Netherlands. Cymer Inc. makes excimer lasers that mix gases to produce deep ultraviolet (DUV) light. The term - excimer - combines "excited" with "dimer," a molecule with two atoms. Cymer develops specialized light sources used in semiconductor manufacturing. Cymer's excimer light sources provide deep ultraviolet photolithography sources used as a key part of chip manufacture. Cymer is the world's leading supplier of excimer laser illumination sources, the essential light source for deep ultraviolet (DUV) in photolithography systems used in the manufacture of semiconductors. Cymer's excimer lasers constitute a substantial majority of all excimer lasers incorporated in DUV photolithography tools. Cymer's customers include all five manufacturers of DUV photolithography systems: ASM Lithography, Canon, Nikon, SVG Lithography and Ultratech Stepper. Photolithography systems incorporating Cymer's excimer lasers have been purchased by each of the world's 20 largest semiconductor manufacturers. Semiconductor makers incorporate the company's lasers into their photolithography equipment because DUV technology allows the chip makers to put more circuits on a chip and to produce more chips.