ASML is the leader in lithography systems for manufacturing semiconductors with 90% market share. Lithography is the process in which a light source is used to expose circuit patterns from a photo mask onto a semiconductor wafer. Lithography allows chipmakers to increase the number of transistors on the same area of silicon, with lithography historically representing a high portion of the cost of making cutting-edge chips. ASML outsources the manufacturing of most of its parts, acting like an assembler. ASML's largest clients are TSMC, Samsung, and Intel.