A yellow-orange breakdown product of hemoglobin that appears in bruises as they heal, formed from iron-free porphyrin.
From haematoid + -in (chemical suffix). Discovered in the 1800s when scientists studied bruise healing and found this distinctive pigment.
Haematoidin is why old bruises turn yellow-green—it's what remains after your body breaks down hemoglobin, and forensic pathologists can use its color to estimate how long ago someone was injured.
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