Autoclaved Aerated Concrete [AAC], a revolution in thermal insulation and energy-efficient construction, was invented by Dr Axel Eriksson in Sweden in 1923. He developed a process for curing a special mixture of lime, metal powder, and a substance containing silica. The resulting steam-cured concrete had good thermal insulation, relatively high strength, high fire resistance, and could be produced economically. Carl August Carlén, who ran a family business, was granted a license to produce AAC in 1928. After a successful introduction in Sweden, AAC production became international in 1937. The use of license systems allowed third companies to invest in AAC, leading to rapid international expansion. Germany and Poland became leading centres of expertise and allowed AAC to expand on a global scale. As we approach the era of regulatory measures to meet Europe’s climate change targets AAC plays a significant role. This article presents the history and development of autoclaved aerated concrete over the last 100 years. The most important issues concerning the standardization of the production and use of autoclaved aerated concrete are also discussed.