Glass, in a way, is both natural and man-made. The first traces of glass were formed naturally by volcanoes and lightning strikes. This occurred as a result of natural rocks and sand reaching extremely high temperatures then cooling rapidly and solidifying. This type of glass is normally green or bluey green.
Man discovered this and began producing glass artificially as far back as the second millenium BC by the Egyptians. This early glass, was much less common than today and very precious.
At the end of the first century BC, the method of glass blowing was discovered. This made glass far more plentiful and affordable for everyday people.
The 12th Century AD saw the development of stained glass which was mainly used for cathedrals and monestries. During the 13th Century, Venice became the major glass producer.
The 17th Century saw another revolution in glass manufacturing. An Englishman, George Ravenscroft, discovered that adding lead to glass made it sparkle far more than it had previously.
Glass can be used for many household objects as well as Art Glass which is popular for designers such as Lalique and Tiffany.