From Owen Jones' Grammar of Ornament compiled in the middle of the nineteenth century to the discovery of quasicrystals in the late twentieth century and Lu and Steinhart's and others' explorations of decagonal and quasiperiodic tiles in Islamic monuments of Iran, the interpretation of ornament in Islamic architecture and the arts has undergone profound reassessment during the past 150 years. Broad-ranging questions concerning the universality of geometry that Oleg Grabar raised in his Mediation of Ornament, and the probing studies of Alpay Özdural in the 1990s on architectural ornament, as well as Gülru Necipoğlu's historical exposition of The Topkapi Scroll have contributed to a shift from assuming that ornament is ornamental to questioning and considering the underlying mathematical nature of ornament as well as the cultural specificity of its uses in Islamic art.