This lecture explains how skyscraper design developed in the 20th century due to city regulations, new technologies, and changing architectural ideas. It introduces the 1916 New York Zoning Resolution and the setback principle, which influenced the stepped form of early tall buildings and helped bring light and air to streets below. The lecture discusses important examples such as the Chrysler Building by William Van Alen, the Empire State Building by Shreve, Lamb & Harmon, Lever House by Gordon Bunshaft (SOM), and the Seagram Building by Mies van der Rohe. It also explains how ideas like open plazas, minimalism, and corporate identity shaped modern skyscrapers and continue to influence urban skylines worldwide.