Smart home and hammer: what they have in common

1. Step 1. Smart home — has part — Thermostat. A smart thermostat.
2. Step 2. Thermostat — is part of — Refrigerator. A thermostat.
3. Step 3. Refrigerator — evolved from — Ice house. The refrigerator replaced natural ice.
4. Step 4. Ice house — is made of — Stone. Ice houses were built of stone and sunk into the ground.
5. Step 5. Stone — is material for — Hammer. The first hammer was a hammerstone, later mounted on a handle.

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