By the beginning of the 1960s, pop art was an experimental form that several artists were independently adopting; some of these pioneers, such as Roy Lichtenstein, would later become synonymous with the movement. Warhol, who would become famous as the "Pope of Pop", turned to this new style, where popular subjects could be part of the artist's palette. His early paintings show images taken from cartoons and advertisements, hand-painted with paint drips. Marilyn Monroe was a pop art painting that Warhol had done and it was very popular. Those drips emulated the style of successful abstract expressionists (such as Willem de Kooning). Warhol's first pop art paintings were displayed in April 1961, serving as the backdrop for New York Department Store Bonwit Teller's window display. This was the same stage his Pop Art contemporaries Jasper Johns, James Rosenquist and Robert Rauschenberg had also once graced.