What was M.C. Escher's eye done in?

M.C. Escher's famous work titled "Eye" was created in 1946 using lithography, a printmaking technique that involves drawing on a flat stone or metal plate. The artwork features a highly detailed, surreal depiction of an eye, reflecting Escher's fascination with perspective and optical illusion. The piece exemplifies his unique ability to blend mathematical concepts with artistic expression, creating intriguing visual experiences.