These three factors led architects to seek an honest, economical, and utilitarian style of architecture that could make use of the new building methods and materials being developed, while still satisfying aesthetic taste. Technology was a critical factor here; the new availability of cheap iron and steel, together with the discovery in the late 1880s and 1890s of the steel skeleton structure, made the traditional brick and stone building techniques obsolete. In addition, architects began using steel-reinforced concrete for floors and other secondary support elements, and fenestrating the exteriors of buildings with glass. The resulting austere and disciplined architecture was thus formed according to the principle that modern buildings should reflect a clear harmony between appearance, function, and technology