Although the principle of stimulated emission of light is known for over a hundred years it took several decades for the use of lasers in medicine. First lasers werde used with wound healing problems, later for patients suffering from musculoskeletal pain. Recent developments use not only red and infrared laser for photobiomodulation but employ also other wavelengths (blue, green), and intensities up to 1000 mW. The latest innvoation is the radiation of blood by hemolaser devices which seem to have beneficial effects on rheumatic diseases, diabetes, and Long COVID symptoms, respectively. The evidence base is growing rapidly.