Diagrids are load-bearing structures made of steel diagonal grids. They were first used in the great buildings of the turn of the millennium, such as the Swiss Re Tower in London (“The Gherkin”) and the Hearst Magazine Tower in New York City. Dagrids owe their ensuing popularity not only to their stunning aesthetic value, but also to their very tangible benefits: lateral loading capacity, a massive saving of material, a significant gain in open, usable floor area, and increased flexibility. At its opening in 2014, the Leadenhall Building in London will be the first skyscraper without a bearing inner core—thanks to a diagrid structure. This book explains comprehensively for the first time all of the aspects involved in this new bearing structure. The author, experienced in teaching, research, and practice (recent publication: Understanding Steel Design. An Architectural Design Manual, 2011), has tracked the development of this technology from its beginnings and employs photographic documentation of the construction phases of many diagrid structures.