An important aspect artists must consider is materiality. The line between natural and artificial in the context of art is meaningful because it hugely influences the meaning one assigns to a piece. In some ways the difference can be described very clearly, for instance when "Land Art" came about in 1960s, and as Judith Collins explains, artists "turned to working outside [on] the land, rather than in their studio, partly as a reaction to the urban materialist Pop Art that was prevalent at the time." It is clear in this context that the use of nature and natural materials outside in art can be considered the polar opposite of the artificial materials that were used in some artists' studios.