Vacuum glazing is an innovative transparent thermal insulator that has applications in high performance windows. Two sheets of glass are separated by an evacuated space maintained by a regular array of support pillars, and the structure is sealed around the edges with solder glass or a metal bond. The evacuated internal gap reduces the heat transfer across the glazing by eliminating air conduction and convection between the glass sheets. This review paper traces the development of vacuum glazingfrom the initial proposal 100 years ago, to the first reported manufacture in 1989 by the University of Sydney, the subsequent commercialisation of that design in 1996 and recent advances. The various design challenges are discussed along with the innovative ways they were successfully addressed by two research groups. Several key non-technical factors that have been equally important to the commercialisation and acceptance of this new technology are also presented. The future prospects for vacuum glazing are discussed in the context of the growing interest in energy efficient buildings and higher standards for the thermal performance of windows.