Stereolithography (SLA or SL; also known as Optical Fabrication, Photo-Solidification, Solid Free-Form Fabrication, Solid Imaging, Rapid Prototyping, Resin Printing, and 3D printing) is a form of additive manufacturing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photopolymerization, a process by which light causes chains of molecules to link together, forming polymers. Research in the area had been conducted during the 1970s, but the term was coined by Charles (Chuck) W. Hull in 1986 when he patented the process. He then set up 3D Systems Inc to commercialize his patent.