This History of Stained Glass
The earliest known use of stained glass was man made beads created by the Egyptians in 2750 and 2625 BC. The beads were made by winding a string of molten glass around a removable clay core, creating glass that was opaque and precious. Colored glass fragments have been found in so many wonderful colors and shapes by archaeologists around the world. 
Colored glass was commonly used in churches to create not only windows, but mosaics as well. San Vitale Basilica in Ravenna, Italy, remains the home for an apse mosaic that dates from 526 to 547 AD. The mosaic shows Christ the Redeemer sitting on the sphere of the world, with San Vitale, two angels, and the founder of the church, Bishop Eccleius. There are many mosaics to see in the Basilica. The arch that marks the entrance into the presbytery, which is covered in multiple works of art, and the presbytery, which is fully decorated with numerous mosaics on the walls and ceilings, are examples that can still be seen today.
The Hagia Sophia church, originally built in 532 and 537 AD, is now a museum in Instanbul, Turkey. The building itself has been destroyed and resurrected numerous times. Many of the original mosaics were destroyed or covered in plaster, in 1453 when the building was converted into a mosque. When the building was restored in 1847-1849, many of the mosaics were rediscovered, but the destroyed by an earthquake in 1894. In the 1930s during restoration, another large number of mosaics 
were discovered, but due to Hagia Sophia's long history as both a church and a mosque, it was difficult to uncover the mosaics without destroying the historic Islamic art. The restoration debate is ongoing.
The Romans are believed to be the first to glaze the glass into windows, sometime in the first century AD. Their first attempts at creating such art work were irregular and not very transparent. Colored glass creation took time and artistic skills. Both Egyptian and Roman artisans eventually excelled in the process and were able to create beautiful small colored glass objects. Two such objects, the Lycurgus Cup and the Portland Vase, are held at the British Museum.
St. Paul's monastery is where one of the oldest known windows made of multiple pieces of colored glass was unearthed. That church was founded in 686 AD in Jarrow, England. Unfortunately, the original windows were probably destroyed when Vikings sacked the church and monastery in 794 AD.
The Augsburg Cathedral in Augsburg, Germany, was founded in 944 AD. The cathedral's stained glass windows date from sometime in the 12th century. In a severe but colorful style, they depict Old Testament prophets Moses, Hosea, Daniel and Jonas. You can still see these awesome creations, as well as other beautiful sculptures and carvings, if you visit the church.
