The role of glass in buildings has evolved dramatically over the last 25 years with greater performance demands placed on its design and operation in buildings. Low-E glazings now dominate markets, with still better insulating glazings commercially available. As architects and owners design even larger glass areas for light and view, the performance challenges from cooling loads and glare increase. Industry responded with static spectrally selective glass to reduce solar gain but provide daylight and these now dominate market offerings. However no static coating can serve all needs. The holy grail for optimizing energy, comfort and view is a “smart” glazing whose properties are dynamically controlled across a wide range. The underlying research and early smart glass prototypes were demonstrated over 25 years ago, and viable products are now commercially available and compete with motorized shading. But smart glass products have captured only niche markets to date. We outline these past market and performance trends in the context of the next 25 years of development, with competing coating and shading technologies, the logistics of integration with other building systems and the challenges to deliver and maintain proper operations over a range of climate conditions, and building and user requirements.