Tiles were used to decorate monuments from early ages in Iran. Mosaic patterns were the first step in the evolution of tile decoration. Imaginative and creative artisans put together mosaic patterns using bits of colored stone and brick and created patterns of triangles, semi-circles and circles in harmony with the structures they were placed on. These patterns later evolved into design of natural subjects, such as plants, trees, animals and human beings.
In the Achaemenian period full use was made of glazed and decorated fired bricks in yellow, green and brown on the palaces of Susa and Persepolis. Fired and glazed bricks were an important advancement in tile technique. The "Eternal Soldiers" at Persepolis have long elegant gowns in glaze made of fired earth and plaster.
Glaze was used on vessels and even coffins in the Parthian period, but little architectural evidence has been discovered to show that glazed bricks were used. Turquoise and light green glaze were the most popular colors. Fresco painting was more popular for the decoration of buildings
The art of tile working blossomed in the Islamic period of Iran. It became the most important decorative feature of religious buildings. Iranian tile makers were in great demand and worked in the far corners of the Islamic empire.
The next stage of development was the use of colored glaze on decorative brick; turquoise being the most popular color. Pieces of turquoise glazed bricks were used with decorative brick works on monuments from the Saljuq period onwards.
So artisans were familiar with the technique of manufacture of glazed bricks by this time. Sometimes these turquoise glazed bricks were used to create Kufic inscription among the brick patterns or were scattered among the brick patterns.
Mongol invasion slowed and halted many artistic traditions and trends. Normal conditions only returned by the 13th century CE, when the Ilkhanid rulers accepted Islam; they also became interested in creating secular and non-secular monuments and buildings. By this time, decorative bricks and tiles were used not only on the exterior, but also inside the building to cover the walls and domes.
It should be mentioned that the technique of tile and its secrets of trade were safely guarded and orally handed from father to son and master to student; thus rarely have designs, patterns and details of technique been documented and few complete treatises exist on the art of Iranian tile work in the past.