Published in 1543, at the height of the Renaissance, it is an exhaustive visual atlas and verbal description of human anatomy based in part on the author's own dissections; its massive Latin text of over 700 folio pages contains extensive descriptions of the tools and techniques of dissection, as well as of the structures of the human body those tools and techniques reveal. The whole is illustrated by a remarkable series of woodcuts from the circle of Titian. A book of great intellectual complexity and physical beauty, it was also a work of daring, reflecting Vesalius' youthful ambition—he was only twenty-eight when he completed it—and his desire to use the new technology of printing and most progressive artistic conventions of the period to push the edges not only of contemporary anatomical knowledge but also of contemporary attitudes toward the human body. To a modern reader, the most striking and original aspect of the Fabrica is its heavy reliance on images. They were based on meticulous observation of dissected cadavers, and Vesalius married them clearly to his text, using an elaborate system of captions, cross references, and marginal annotations, which made them an integral part of his presentation. Furthermore, the illustrations were works of art in their own right; even the simplest far exceeded all previous anatomical images in clarity and detail (with the exception of some of the unpublished anatomical drawings of Leonardo da Vinci), and the more elaborate were extraordinary for their beauty and the imaginativeness of their conception. Commentary by Katharine Park, essay on historiated initials.