Minimalism or Minimal art is an extreme form of abstract art that developed in the USA in the second half of the 1960s. It can be seen as extending the abstract idea that art should have its own reality and not be an imitation of some other thing. It picked up too on the Constructivist idea that art should be made of modern, industrial materials. Minimal artists typically made works in very simple geometric shapes based on the square and the rectangle. Many Minimal works explore the properties of their materials. Minimal art was mostly three-dimensional but the painter Frank Stella was an important Minimalist. The other principal artists were Andre, Flavin, Judd, Lewitt, Morris, and Serra. There are strong links between Minimal and Conceptual art. Aesthetically, Minimal art offers a highly purified form of beauty. It can also be seen as representing such qualities as truth (because it does not pretend to be anything other than what it is), order, simplicity, harmony.