Parking meter and vacuum pump: what they have in common

1. Step 1. Parking meter — evolved from — Vending machine. A payment machine.
2. Step 2. Vending machine — includes — Arcade machine. A coin-operated machine.
3. Step 3. Arcade machine — has part — Cathode-ray tube. A CRT monitor.
4. Step 4. Cathode-ray tube — evolved into — Electron. Thomson discovered the electron in cathode rays.
5. Step 5. Electron — is used in — Electron microscope. A beam of electrons instead of light.
6. Step 6. Electron microscope — has part — Vacuum pump. A vacuum in the column.

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