Along with Robert Rauschenberg, Jasper Johns was a key figure in the development of Pop Art. Johns stunned the art world in 1954-55 when he painted an American flag, not "within" a painting but "as" a painting. Later, he included targets, numbers, maps, and letters in his repertoire. Johns used encaustic, a medium combining wax, resin, and pigments, and mixed it with collage elements to yield a richly textured but transparent surface that allowed him to reveal the process and fabric of his creation. By rendering traditionally flat signs such as targets or flags with heavily textured brush strokes, Johns emphasized their transformation into works of art.