If pure visual impact is a key element in Modern art, then Roy Lichtenstein's prints fittingly rank amongst the most successful and sought-after images of the 20th century. As with Andy Warhol, with whom he jointly championed the 'New Realism' movement, or 'Pop Art' as it came to be known, Lichtenstein was fascinated with the world of commercial printing and how the industrial processes involved actually influenced the way images were delivered to a wide audience. Lichtenstein's instantly recognisable visual style adapts techniques used in mass-production in order to re-enforce powerful and accessible images. He himself recognised Sweet Dreams Baby (lot 556) as one of the quintessential examples of Pop Art, with its restrained palette and the use of a broken surface of dots, dashes and black outlines, which are a direct adaptation of the Benday screen used in industrial printing. Lichtenstein's visual dialect is particularly striking in the images he himself chose to promote his work at the Leo Castelli Gallery in New York where the same colour schemes and surface patterns enhance the comic strip violence (such as in Crack!, lot 550) or romantic irony (Crying Girl, lot 549). Lichtenstein's mature works retain the irony and the striking visual characteristics of Pop Art, but the subject matter is more monumental, covering the classical subjects of art, such as the Nude (Nude, lot 562 and Nude with Blue Hair, lot 563) or Landscape (View from the Window, lot 561 or Liberté, lot 558) and the techniques and colour schemes have become more complex and subtle as the artist demonstrates his consummate knowledge and skill as a printmaker.