The early stages of modern architecture developed from 1850-1900 with the rise of iron and steel frame construction. This allowed for taller, wider buildings like the Eiffel Tower and Crystal Palace. In Chicago, architects pioneered the steel-framed skyscraper like Louis Sullivan, who coined the phrase "form follows function." The Chicago School emphasized plain designs with reduced ornamentation that accelerated the modern aesthetic. Sullivan was influential in developing the modern style through his organic yet geometric designs.