This lecture explains advanced structural systems used in modern and supertall skyscrapers, focusing on how buildings resist wind, earthquakes, and extreme loading conditions. It begins with the Citicorp Center, New York, designed by Hugh Stubbins with structural engineer William LeMessurier, highlighting how site constraints led to innovative solutions such as central columns and inverted chevron bracing. The lecture then introduces the bundled tube system, using examples like the Willis Tower (Sears Tower) by Bruce Graham / SOM, explaining how multiple tubes work together to provide strength and efficiency in very tall buildings. It further discusses hybrid structural systems, tube-in-tube systems, and high-strength concrete cores, with case studies including One World Trade Center by SOM. The session also covers superslender skyscrapers, using 432 Park Avenue, New York, to explain concepts such as slenderness ratio, tuned mass dampers, blow-through floors, and core–perimeter interaction. Finally, the lecture introduces exoskeleton structures, megaframes, and future structural ideas, helping students understand how structure, safety, efficiency, and architectural form come together in contemporary skyscraper design.