The mosaics inside Hagia Sophia caught the light and would shimmer, making for even more dramatic lighting to emphasize the message of God's greatness. The mosaics had to be large and clearly visible, as well as brightly colored, and they had to be recognizable Bible stories. As stated before, the Byzantine artists' intention was to glorify Christianity (actually, it's very Catholic, but I'll get to that later); their works are flat, stiff, and unrealistic because it was necessary to portray clear and simple religious lessons to the illiterate. They did not aspire to create beautiful and graceful figures like the Greeks. Their pictures were meant to be humble, paying homage to God for salvation, and clearly presenting the Gospel message without giving any attention to superfluous and irrelevant aesthetic elements.