What is this close-up picture? (WotsThat: Smartwatch heart rate sensor)

Question

What object is shown in this zoomed-in close-up photo?

MalachiteRun · Accepted Answer

Smartwatch heart rate sensor. Smartwatch heart rate sensors use LED light to detect blood flow through your wrist, similar to how pulse oximeters work. Some advanced models can track irregular heartbeats and alert you to potential health concerns before you'd notice symptoms yourself.

Answer: Smartwatch heart rate sensor

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