Human hair strand and steam locomotive: what they have in common

1. Step 1. Human hair strand — is part of — Hygrometer. The length changes with humidity.
2. Step 2. Hygrometer — has part — Spring. The tension of the hair.
3. Step 3. Spring — is part of — Bogie. Spring suspension.
4. Step 4. Bogie — is part of — Diesel locomotive. Bogies with wheelsets.
5. Step 5. Diesel locomotive — evolved from — Steam locomotive. It replaced the steam locomotive.

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