The light bulb.
Timothy H
TH
McCalmont
D003872:Dermatitis / Q000209:etiology / Q000235:genetics / Q000473:pathology; D004427:Ear Diseases / Q000209:etiology / Q000235:genetics / Q000473:pathology; D004817:Epidermis / Q000473:pathology*; D006801:Humans; D018329:Nevus, Blue / Q000209:etiology / Q000235:genetics / Q000473:pathology; D018332:Nevus, Epithelioid and Spindle Cell / Q000209:etiology / Q000235:genetics / Q000473:pathology