Mosaic is the art of creating images with small, square stones or colored glass. It is a decorative technique that has its origins in Mesopotamia. At least, that was the place where mosaic was first found. Then the colored stones were used in the times of Sassanid Empire and under the Roman influence. Hagia Sophia in Istanbul is richly decorated with mosaics that represent Virgin Mother, Jesus, saints, or emperors and empresses or simply, just decorative patterns. During time, the mosaics were vandalized and parts of them were shipped to Venice to the doge. Later, the mosaics were covered with plaster when the building was transformed into a mosque, due to the fact that Islamic cultures are against representational imagery. The last mosaic on the bottom of the page is the most famous and the finest in Hagia Sophia. Deësis mosaic has soft features and beautiful colors. The style is close to Italian paintings. This mosaic is considered as the beginning of the Renaissance in Byzantine pictorial art.