To make the vaults safer, the French architects added external buttresses. They were placed on the outside of the cathedrals to give support to the building by taking the weight of the building off the walls and transferred it directly to the ground. Since the buttresses appeared to be suspended, they were called "flying" buttresses. The use of stained glass windows in the Gothic cathedrals represented expressions of religious beliefs. 0 have massive stained glass windows, it is necessary to have thin walls. The walls could be thin because of the flying buttresses. Also, the thin walls could go to a new height while the thicker walls of the Romanesque period could not. The function of the window was not only of beauty, but also to illustrate biblical events so that the people who came to worship in the cathedrals could learn the stories of Jesus and other prophets. "The glass fragments used in the stained glass windows were referred to as gems, a reflection of a pre-Christian belief that glass us brought to life by the sun's rays." The light is what brings the stained glass windows to life by letting the heavenly light into the place of worship. Religion was an important factor in the shift between Romanesque and Gothic. During the middle ages, the catholic religion was very powerful andplayed an important role in everyone's life. The Gothic Cathedrals were the central place of worship. They were