Contemporary architecture is the architecture of the 21st century. No single style is dominant; contemporary architects are working in several different styles, from postmodernism and high-tech architecture to highly conceptual and expressive forms and designs, resembling sculpture on an enormous scale. The different styles and approaches have in common the use of very advanced technology and modern building materials, such as tube structures which allow construction of buildings that are taller, lighter and stronger than those in the 20th century, and the use of new techniques of computer-aided design, which allow buildings to be designed and modeled on computers in three dimensions, and constructed with more precision and speed.