Robert Wilhelm Bunsen (1811–1899), one of the greatest experimental chemists of the 19th century, was a professor at Heidelberg University between 1852 and 1889. He and Professor Gustav Kirchoff invented the spectroscopy, the analysis of the light emitted by heated elements. Using the spectroscopic technique, he discovered the elements of cesium and rubidium. He also invented the Bunsen burner, a laboratory gas burner that produces a clean, hot flame and remains a standard piece of scientific equipment.