Incubator and gutenberg printing press: what they have in common

1. Step 1. Incubator — is made of — Clay. Egyptian incubators were clay chambers.
2. Step 2. Clay — is material for — Movable type. Bi Sheng’s type was made of fired clay.
3. Step 3. Movable type — is part of — Gutenberg printing press. Text is set from metal type.

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