An energy-sensitive material used in lithography. Resists are applied to the substrate material as a thin film and selectively exposed to an energy beam (light, electrons, etc.), which causes chemical changes in portions of the resist. The exposed film is then developed to selectively remove either the exposed portions (positive resist) or the unexposed portions (negative resist). See also photoresist; electron-beam lithography; X-ray lithography; ion-beam lithography.