Hat and lead–acid battery: what they have in common

1. Step 1. Hat — is made of — Felt. Felt.
2. Step 2. Felt — is material for — Piano. The hammers are covered with felt.
3. Step 3. Piano — has part — Keyboard. A keyboard.
4. Step 4. Keyboard — is part of — Laptop. The keyboard is built into the laptop's case.
5. Step 5. Laptop — has part — Lithium-ion battery. A battery.
6. Step 6. Lithium-ion battery — evolved from — Lead–acid battery. The lithium-ion battery is the next generation of rechargeable chemical current sources, with higher specific energy.

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