Aerosol can and electronic calculator: what they have in common

1. Step 1. Aerosol can — has part — Valve. A valve.
2. Step 2. Valve — is part of — Gas lamp. A gas supply valve.
3. Step 3. Gas lamp — evolved into — Street light. Gas lamps.
4. Step 4. Street light — has part — LED. LEDs.
5. Step 5. LED — is part of — Liquid-crystal display. LED backlighting.
6. Step 6. Liquid-crystal display — is part of — Electronic calculator. An LCD display.

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