Niels Ryberg Finsen who won the Nobel Prize in Medicine in 1903 for introducing phototherapy for lupus vulgaris. He was only the third laureate in medicine, after Emil von Behring (1901) and Ronald Ross (1902), and the first for outstanding achievements in the field of dermatology. Several thousand lupus vulgaris patients from different European countries were treated in the Medical Light Institute in Copenhagen, founded by Finsen, from 1896 until his death in 1904. Until the tuberculostatic drugs were introduced in the middle of the 20th century, the "Finsen Exposure" was the only effective therapy of lupus vulgaris. The carbon arc lamp initially used by Finsen was later modified and then eventually replaced by the mercury quartz lamp developed by Arons. Today Finsen is rightly recognized as the founder of the modern dermatological phototherapy.