Sometim around the 2nd century AD, the Egyptians had effectively established a monopoly on papyrus because of the massive usage at the Library of Alexandria's annexes (after destruction of the main campus). The Greek city of Perma reacted by developing a material of their own from stretched animal skins. This sheet became known as parchment (and sometimes vellum).
The preparing process of the animal skins would sometimes cause holes and tears to form in the pages. Scribes quickly learned to just work around the imperfections.
The development of parchment did not significantly decrease the cost of manuscript page production, but it did make the blank pages more readily available to scripts and amanuenses (i.e. transcribers) throughout Europe, the Middle East, and North Africa.
Since parchment came well after codices started to become the document format of choice, the vast majority of surviving parchment manuscripts are in codex form. The most well-known ancient codex of parchment is, arguably, the Codex Sinaiticus, which came from St. Catherine's Monastery at the foot of Mt. Sinai in Egypt. It is estimated to have been written around the year AD 325 with the entire Old Testament and New Testament, plus a few Apocrypha books. The New Testament portion still exists in its complete form.
By @HullBreach
