The Cairo geniza was a storeroom for no longer usable holy books in the synagogue of Fustat, Old Cairo, where for centuries, old Jewish manuscripts, mostly in Hebrew, Aramaic, and Judeo- Arabic, including also secular documents and communal records, were deposited. In the 19th century, European scholars became aware of this collection and manuscripts were removed to a variety of libraries in Europe and the United States. This material provides those studying the ancient world and ancient Jewish texts in particular with an amazing treasure of documents, throwing light on the history of the biblical text and its interpretation, the Hebrew language, Greek and Syriac versions of the Bible, Second Temple and Rabbinic literature, Jewish liturgy and the later history—political, economic, and religious—of the Jews in the Mediterranean basin. This material has totally reshaped our understanding of these fields. In the area of Bible, these texts illustrate the manner in which the vocalization and cantillation symbols were developed. Hebrew versions of some important Second Temple literature, later found among the Dead Sea Scrolls, had earlier been discovered in the geniza. Many previously unknown Midrashim and rabbinic exegetical materials have become known only from this collection. This material has provided an entirely new corpus of liturgical poetry.