During the past few decades, what is now formally known as open building has progressed through several stages. Initially, Open Building constituted a set of speculative principles and aspirations that led to research, followed by a number of built projects in several countries. In the second stage, open building began to be initiated by clients asking for open buildings – certainly in office and retail markets where this practice has long been conventional and unremarkable – but increasingly in housing and healthcare facilities in a number of countries. In the third stage, open building came to be public policy. During all these stages, research (in academia, government and industry) and teaching has continued on a wide range of open building issues – including design methods, finance, technology, and user engagement.