Schooten read Descartes's Géométrie (an appendix to his Discours de la méthode) while it was still unpublished. Finding it hard to understand, he went to France to study the works of other important mathematicians of his time, such as François Viète and Pierre de Fermat. Returning to his own city of Leiden, he became a professor of mathematics, his most important pupil being Christiaan Huygens. Very important was his commentary on the Géométrie, which made the work understandable to the broader mathematical community, and thus was responsible for the spread of analytic geometry to the world. Schooten's efforts also made Leiden the centre of the mathematical community for a short period in the middle of the 17th century.