The importance of tilework in Persian architecture arises from two important factors; first the need to weatherproof the simple clay bricks used in construction, and secondly the need to ornament the buildings. Tilework was used to emphasise certain motifs such as the ascending and descending patterns in the dome of the Sheikh Lotfallah mosque, and to emphasise transitional points in the design either by providing a patterned panel or border, or by incorporating calligraphy.
Two main types of tilework developed. The mosaic tilework formed by incorporating single colour tiles into the design and the so called cuerda seca technique where a range of colours is used on individual, generally square shaped tiles. This latter form developed extensively during the 17th century, Safavid dynasty, as the quality of glazes improved and because it was significantly cheaper to produce.
The principle colours used were blue, yellow, turquoise, pink, aubergine and green. These seven colours gave rise to the name haft rang - which literally means "seven colours"