Which innovative product technology is credited with first making the Bible widely accessible to the general public in the 15th century?

Throughout history, religious texts have undergone significant transformations in how they're produced and distributed. From handwritten scrolls to mass-printed books to digital applications, the 'product design' of sacred texts reflects both technological innovation and changing spiritual practices. This trivia question focuses on a pivotal moment in the history of religious text production that dramatically changed accessibility and religious practice worldwide.

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Gutenberg's movable type printing press
Wooden block printing from China
Illuminated manuscript techniques
The codex book format (replacing scrolls)