How can we hope to understand Islam without knowing how its founding text, the Qurʼān, took shape and then crystalized? The discovery of a palimpsest in Sanaa in 1973 confirmed the existence of other recensions of the Qurʼānic text in the first centuries of Islam. Studies of these documents and of the manuscripts of the predominant transmission have made it possible to identify the various strata of texts and the variants that were gradually excluded. This unprecedented approach to the Qurʼān profoundly renews the intellectual and cultural history of the Muslim world.