Among the works composed by Photiosthe captain of the guard, ambassador and chief imperial secretary who served two terms as patriarch under the emperors Michael III and Basil Iis one known as the Myriobiblos (the 'Myriad Books') or Bibliotheca (the 'Library'). A huge endeavour, it consisted of around reviews of varying length that summarised the content of a text or group of texts, and provided remarks on the style as well as biographical details of the authors. Assuming knowledge of works that were considered canonical and therefore used as textbooks, Photios explicitly excluded these from discussion. Instead, his reviews represented forays further afield, pointing to the voracious breadth of his interests. Theological writings dominated, as one would expect of an ecclesiastic, but secular works of greater or lesser antiquity, including a number of considerable rarity, were not neglected: alongside reviews of philosophical disquisitions, histories, biographies, novels, and poems there are ones of scientific compendia such as lexica, medical treatises, herbals, and agricultural manuals. The quality of the collections to which Photios had access is evident from the fact that he often constitutes our fullest or indeed only source for an ancient text. In many instances, he consulted multiple versions, making an effort to seek out reliable, old manuscripts. Where he could secure access to only a fragmentary copy of a particular work, or had to abandon reading it before he had finished, he would leave space at the end of his draft review in the hope he could return to the task later. There were occasions, too, when he appears to have produced a preliminary evaluation based solely on others' excerpts and summaries.In some cases at least, he explicitly acknowledged that he had not yet managed to find or read the text in question. Unless otherwise indicated, all translations from the Greek are the work of the author of this chapter.