Mercury and fitness tracker: what they have in common

1. Step 1. Mercury — is material for — Thermometer. Mercury thermometers.
2. Step 2. Thermometer — includes — Infrared thermometer. A pyrometer is a thermometer that measures temperature at a distance by infrared.
3. Step 3. Infrared thermometer — uses — Infrared radiation. The infrared radiation of a body.
4. Step 4. Infrared radiation — is used in — Pulse oximeter. Infrared absorption by haemoglobin.
5. Step 5. Pulse oximeter — is part of — Fitness tracker. An optical heart-rate sensor.

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