[en] During the excavations of early magnate buildings, Pre-Christian Cult Sites and early trade centre, several fragments from windows glass have been found. Until recently, fragments of window glass from Pre- Christian Sites were most often regarded as modern glass, or as a kind of "pollution" in the excavated fields. Our research and analyses show that windows with glass were used in pagan temples and in the estates of the elite already in the early Viking ages. Although glass windows were not common in Viking Age Scandinavia, our research shows that glass window may have existed in royal estates in the Viking Age in Pre-Christian Cult places and temple buildings. It is interesting that glass window appears in Scandinavia long time before they were believed to exist, and especially in areas where glass windows was not used in buildings until recently. The presence of window glass in early magnate residences, on Pre-Christian cult Sites and at early Viking trade centre seems to draw an interesting pattern. Most probably glass windows in Pre-Christian Scandinavia, were used in the same way as in early Frankish and Anglo-Saxon churches. We present here some results on window glass originating from : - Pre-Christian Cult Sites : Tissø and Strøby Toftegård on Sealand, Sorte Muld on the island of Bornholm, and from Uppåkra in Scania, - as well as Viking Age sites : Haithabu in northern Germany, Kaupang in Norway, and Birka in Sweden, These window glasses were all analysed using Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) at the Centre Ernest-Babelon, (CNRS, Orléans, France). Our results show the presence among our corpus of three main type of glass compositions : natron glass, woodash glass and woodash lime glass. If natron glass illustrates the re-use of ancient antique windows, the presence of woodash and woodash lime glass enabled us to put new light on the use of early glass windows in Southern Scandinavia.