For a thousand years, a European Christian who wanted to read the New Testament in its original Greek had to find a Greek manuscript and a reader willing to work through it by hand. Desiderius Erasmus changed that permanently in 1516, when the Basel printer Johann Froben published his edition of the Greek New Testament, the first ever to reach a printing press, alongside Erasmus's own new Latin translation and critical notes explaining his choices against the entrenched Vulgate text. The edition was, by Erasmus's own later admission, rushed: he worked from whatever Greek manuscripts he could find in Basel, a handful, none complete and none earlier than the tenth century, and where his sources ran out he simply translated the missing verses back into Greek from the Latin Vulgate, producing Greek readings found in no actual Greek manuscript at all.
The haste had a commercial motive. Erasmus and Froben knew that a rival edition, more careful and more thoroughly prepared, had already been printed in Spain under Cardinal Cisneros's direction and was awaiting papal approval before publication. Getting to market first mattered more, in that moment, than getting every reading right, and the first printing of Erasmus's edition consequently carried enough errors and inconsistencies that he spent several later editions correcting them, an imperfect start to a text that would nonetheless become the working basis for the Protestant Reformation's vernacular Bibles.