Bell clapper hammer and glasses: what they have in common

1. Step 1. Bell clapper hammer — is part of — School bell. It strikes the gong.
2. Step 2. School bell — has part — Electromagnet. An electromagnet strikes the hammer.
3. Step 3. Electromagnet — is used in — Electron microscope. Magnetic lenses.
4. Step 4. Electron microscope — evolved from — Microscope. Overcoming the limit of optics.
5. Step 5. Microscope — evolved from — Glasses. Spectacle makers assembled the first microscopes.

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