The association between temperature and disease is almost as old as medicine itself. After Galileo introduced the thermoscope thermometry evolved slowly and only became established in medicine by the work of Carl Wunderlich in the 19th Century. Thermal imaging began in the beginning of the 19th century with William and John Herschel, but was not developed commercially until World War 2. Today modern infrared imaging systems offer high resolution images of human body temperature, and can be used to quantify sensitive changes in skin temperature in relation to certain diseases, and their response to medication. Computing has dramatically improved the power of thermal imaging, and reliable imaging procedures have been established for medical use of this technique.