Glass test tube and internet: what they have in common

1. Step 1. Glass test tube — is part of — Test tube. A glass tube with a rounded bottom.
2. Step 2. Test tube — is made of — Glass. Glass.
3. Step 3. Glass — is material for — Optical fibre. Silica glass.
4. Step 4. Optical fibre — is part of — Internet. The backbones are optical fibre.

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