Synthetic dye and saw: what they have in common

1. Step 1. Synthetic dye — evolved from — Indigo. Synthesizing natural dyes.
2. Step 2. Indigo — is used in — Jeans. Indigo.
3. Step 3. Jeans — has part — Zip. A zip.
4. Step 4. Zip — has part — Wedge. The slider works like a wedge, bringing the teeth together and pushing them apart.
5. Step 5. Wedge — is used in — Saw. Each tooth of a saw is a small wedge.

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