Assemblage, or sculptural construction utilizing found or mixed materials, was one of the most radical genres invented by the early 20th Century Avant-Gardes. It became a staple of the output of such figures as Marcel Duchamp, Dada's Raoul Haussman, the Constructivist Vladmir Tatlin, and the American Surrealist Joseph Cornell, and it appeared in post-war Pop Art courtesy of Robert Rauchenberg and Jasper Johns.
One the earliest and most powerful examples of what the assemblage can accomplish is Umberto Boccioni's Dynamism of a Speeding Horse + Houses (1915), now part of the Peggy Guggenheim Collection in Venice. A rough, hodgepodge relief in cardboard, wood, paint, paper and metals, its apparent primitivism belies the sophistication of its abstraction. A step ahead of Braque and Picasso even, it threw open the pictoral plane to forge a plastic intermingling of figure, time and landscape (in pursuit of the continuity of matter and subject through speed, a Futurist obsession.)
Due especially to the philosophical discoveries of Gilles Deleuze, the assemblage came to be used in postmodern thought as a metaphor for the complex, entagled institutions of the contemporary world. The idea was that the constituent parts of nations, cities, ecosystems etc. worked together as temporary, discontinuous "machines," but could be always severed and regrafted (reassembled) in new formations.
It's evident that the assemblage still fascinates, and lively artistic production in the field continues. Currently the Charles Taylor Arts Center in Hampton, Virginia is showcasing eye-catching, conceptually rich pieces made by natives of the state. Nancy B. Richard for instance, who often fuses hi and low-tech in her work, employs materials such as paintbrushes, old wooden shoes, glass bottles, yarn and poetic text in "Positive Aspects of Negative." The form that emerges from the chaotic juxtapositions is that of a cart and horse: perhaps harkening back to that venerable patriarch of the assemblage technique.