Heat-sealed seams and rocket: what they have in common

1. Step 1. Heat-sealed seams — is part of — Plastic bag. Heat-sealing of the bottom and sides.
2. Step 2. Plastic bag — evolved from — Paper bag. A replacement for paper.
3. Step 3. Paper bag — is made of — Paper. Paper.
4. Step 4. Paper — is material for — Rocket. The first rockets were paper tubes filled with gunpowder.

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