The first glass panes appeared about 2,000 years ago and were used to "close" building openings, providing protection to their occupants from the weather (wind, rain, cold, etc.) while allowing light to enter.  This remains the main purpose of glass panes today.

For many centuries, of course, the use of glass in buildings was not widespread, while only in the 20th century began a substantial improvement in the efficiency of glass.  
Around the end of the 1940s, the idea of double glazing to improve the thermal insulation of glassworks began to be cultivated, but its real development in Western Europe came with the energy crisis of the 1970s.

Benefiting from the extensive research and development efforts of the last decades, glass, today contributes significantly in all ways, to the comfort level of buildings and especially homes.  Advanced types of glass, such as coated, laminated, etc., now provide high quality solutions in areas such as thermal and solar control, sound reduction and safety. 

Modern windows are made from float glass.  The float glass process is also known as the Pilkington process, named after the British glass manufacturer Pilkington, which pioneered the technique in the 1950s at their production site in St Helens, Merseyside in Great Britain.