The ability to pack large numbers of individual transistors in a small area of silicon has enabled the functionality of modern microelectronics, specifically integrated circuits. This work focuses on photolithography - the method used for patterning nearly all integrated circuits fabricated at present, in which optical methods are used to transfer circuit patterns from master images, called masks or reticles, to silicon wafers. This work can serve as an introduction to the science of microlithography for someone who is unfamiliar with the subject. The reader is expected to have a foundation in basic physics, chemistry, and elementary calculus. The text covers a number of advanced subjects and may be useful to experienced lithographers who seek a better understanding of topics outside their areas of expertise. #Conoverview Of Lithography; Optical Pattern Formation; Photoresist; Modelling And Thin Film Effects; Wafer Steppers; Overlay; Masks And Reticles; Overcoming The Diffraction Limit; Metrology; The Limits Of Optical Lithography; Lithography Costs; Alternative Lithography Techniques. Appendix: Coherence.